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    1. Solve the following L P problem through SIMPLEX method

    Maximize Z = 5x1 + 6x2

    Subject to

    2x1 + 3x2 3000

    5x1 + 7x2 1000

    x1 + x2 500

    x1 and x2 0

    Introducing slack variables, x3 0, x4 0, x5 0, so that the constraints now become equations of

    the form:

    2x1 + 3x2 + x3 = 3000

    5x1 + 7x2 + x4 = 1000

    x1 + x2 + x5 = 500

    Also, z 5x1 6x2 = 0

    Now, constructing Table 1,

    x1 x2 x3 x4 x5 z

    2 3 1 0 0 0 3000

    5 7 0 1 0 0 1000

    1 1 0 0 1 0 500

    _________________________________________

    -5 -6 0 0 0 1 0

    The pivot element should now be determined. For this, first the pivot column is selected which will

    be the one with the most negative element in the objective row which is the fourth row.

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    Here, -6 is the most negative element.

    Now, divide the constant column, which is the last column after the vertical line, with the

    corresponding values from the pivot column and select the smallest non-negative element. The row

    with this smallest non-negative element is the pivot row.

    The values from dividing the constant column with the pivot column are:

    3000 / 3

    1000 / 7

    500 / 1

    Here, 1000 / 7 is the smallest non-negative value. The pivot element will be the element at the

    intersection of the pivot row and pivot column.

    So from Table 1, the pivot element is 7.

    x1 x2 x3 x4 x5 z

    2 3 1 0 0 0 3000

    5 7 0 1 0 0 1000

    1 1 0 0 1 0 500

    _________________________________________

    -5 -6 0 0 0 1 0

    Now the pivot column in Table 1 is made into a Unit Column by converting the Pivot Element to 1

    and the other elements to 0.

    R2 = R2 / 7

    R1 = R1 3R2

    R3 = R3 R2

    R4 = R4 + 6R2

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    Now constructing, Table 2,

    x1 x2 x3 x4 x5 z

    -1/7 0 1 -3/7 0 0 18000/7

    5/7 1 0 1/7 0 0 1000/7

    2/7 0 0 -1/7 1 0 2500/7

    _________________________________________

    -5/7 0 0 6/7 0 1 6000/7

    Since there is a negative value in the objective row, the process should be carried out again by

    finding the pivot element.

    Here, -5/7 is the most negative element in the objective row and dividing the constant column with

    the pivot column gives the following values:

    -18000

    200

    1250

    Here, 200 is the smallest non-negative value and thereby, from Table 2, the pivot element is 5/7.

    x1 x2 x3 x4 x5 z

    -1/7 0 1 -3/7 0 0 18000/7

    5/7 1 0 1/7 0 0 1000/7

    2/7 0 0 -1/7 1 0 2500/7

    _________________________________________

    -5/7 0 0 6/7 0 1 6000/7

    Now the pivot column in Table 2 is made into a Unit Column by converting the Pivot Element to 1

    and the other elements to 0.

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    R2 = R2 / (5/7)

    R1 = R1 + (1/7)R2

    R3 = R3 (2/7)R2

    R4 = R4 + (5/7)R2

    Now, constructing Table 3,

    x1 x2 x3 x4 x5 z

    0 1/5 1 -2/5 0 0 2600

    1 7/5 0 1/5 0 0 200

    0 -2/5 0 -1/5 1 0 300

    _________________________________________

    0 1 0 1 0 1 1000

    Now all the values in the objective row are non-negative.

    Therefore, maximum value of the objective function,

    z = 1000

    when, x1 = 200

    x2 = 0

    x3 = 2600

    x4 = 0

    x5 = 300

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    2. Write the Dual of the Problem 1 and give the economic interpretation of Dual Variables.

    Problem 1: Maximize z = 5x1 + 6x2

    Subject to:

    2x1 + 3x2 3000

    5x1 + 7x2 1000

    x1 + x2 500

    x1 and x2 0

    The above problem is the primal problem in the standard form, which means that the primal

    problem:

    Considers maximization of the objective function.

    Has less than or equal to type constraints.

    Has non-negative constraints on the variables.

    Since the above primal problem is in the standard form, the dual problem can be formulated by

    using the following rules:

    The number of constraints on the primal problem is equal to the number of dual variables.

    The number of constraints in the dual problem is equal to the number of variables in the primal

    problem.

    The primal problem is a maximization problem while the dual problem is a minimization

    problem.

    The profit coefficients of the primal problem appear on the right hand side of the

    constraints of the dual problem.

    The primal problem has less than or equal to type constraints while the dual problem has

    greater than or equal to type constraints.

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    The coefficients of the constraints of the primal problem which appear from left to right are

    placed from top to bottom in the constraints of the dual problem and vice versa.

    Therefore, the corresponding dual problem of the primal problem 1, is,

    Minimise 3000w1 + 1000w2 +500w3

    Subject to:

    2w1 + 5w2 + w3 5

    3w1 + 7w2 + w3 6

    w1 0, w2 0, w3 0

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    3. Write the generalized form of transportation problem as LP Problem. Also explain how to

    solve the degeneracy in transportation problem.

    GENERALIZED FORM OF TRANSPORTATION PROBLEM

    In order to obtain the generalized form of transportation problem, we shall make use of an

    example. A manufacturer operates three factories and dispatches his products to four different

    dealers. The table shows the total units that each factory can supply, the total units required at each

    dealer and the cost of transportation of one unit from each factory to each dealer.

    DEALERS

    FACTORY 1 2 3 4 SUPPLY

    1 2 2 2 4 1000

    2 4 6 4 3 700

    3 3 2 1 0 900

    REQUIREMENT 900 800 500 400

    The total units that factories 1, 2 and 3 can supply are 1000 units, 700 units and 900 units, denoted

    by a1, a2 and a3, respectively.

    The total units required at dealers 1, 2, 3 and 4 are 900 units, 800 units, 500 units and 400 units,

    denoted by b1, b2, b3 and b4, respectively.

    The cost of transportation of one unit from Factory 1 to Dealer 1 is 2, from Factory 1 to Dealer 2 is

    2 and so on.

    A transportation problem is formulated as an LP problem using variables with two subscripts.

    Let,

    X11 = Amount to be transported from Factory 1 to Dealer 1.

    X12 = Amount to be transported from Factory 1 to Dealer 2, and so on until,

    X34 = Amount to be transported from Factory 3 to Dealer 4

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    Let,

    C11 = Cost of Transportation of one unit from Factory 1 to Dealer 1, and so on until,

    C34 = Cost of Transportation of one unit from Factory 3 to Dealer 4

    Then the transportation problem can be formulated as:

    Minimise C11X11 + C12X12 = ..C34X34

    Subject to,

    X11 + X12 + X13 + x14 = a1

    X21 + X22 + X23 + X24 = a2

    X31 + X32 + X33 + X34 = a3

    X11 + X21 + X31 = b1

    X12 + X22 + X32 = b2

    X13 + X23 + X33 = b3

    X14 + X24 + X34 = b4

    X11 0, X12 0,.X34 0

    The generalized form of the above transportation problem in Linear Programming problem can be

    written as:

    m nMinimise CijXij (where, m = number of factories, n = number of dealers)

    i=1 j=1

    n

    Subject to Xij = ai, where i = 1 to mj=1

    m

    Xij = bj, where j = 1 to ni=1

    Xij 0, where i = 1 to m, j = 1 to n

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    DEGENERACY IN TRANSPORTATION PROBLEM

    If a basic feasible solution of a transportation problem with m origins and n destinations has fewer

    than m + n 1 positive Xij (occupied cells) the problem is said to be a degenerate transportation

    problem.

    Degeneracy can occur at two stages:

    At the initial solution.

    During the testing of the optimum solution.

    A degenerate basic feasible solution in a transportation problem exists if and only if some partial

    sum of availabilitys (row) is equal to a partial sum of requirements (column).

    We shall make use of the previous example to solve the degeneracy in transportation problem. A

    manufacturer operates three factories and dispatches his products to four different dealers. The

    table shows the total units that each factory can supply, the total units required at each dealer and

    the cost of transportation of one unit from each factory to each dealer.

    DEALERS

    FACTORY 1 2 3 4 SUPPLY

    1 2 2 2 4 1000

    2 4 6 4 3 700

    3 3 2 1 0 900

    REQUIREMENT 900 800 500 400

    Here, S1 = 1000, S2 = 700, S3 = 900R1 = 900, R2 = 800, R3 = 500, R4 = 400

    Since R3 + R4 = S3 so the given problem is a degeneracy problem.

    Now we will solve the transportation problem by Matrix Minimum Method.

    To resolve degeneracy, we make use of an artificial quantity, d.

    The quantity, d, is so small that it does not affect the supply and demand constraints.

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    Degeneracy can be avoided if we ensure that no partial sum of S i (supply) and Rj (requirement) are

    the same. We set up a new problem where:

    Si = Si + d i = 1, 2, ....., m

    Rj = Rj

    Rn = Rn + md

    DEALERS

    FACTORY 1 2 3 4 SUPPLY

    1 2900 2100+d 2 4 1000 + d

    2 4 6700d 42d 3 700 + d

    3 3 2 15002d 0400+3d 900 + d

    REQUIREMENT 900 800 500 400 + 3d

    Substituting d = 0.

    DEALERS

    FACTORY 1 2 3 4 SUPPLY

    1 2900 2100 2 4 1000

    2 4 6700 40 3 700

    3 3 2 1500 0400 900

    REQUIREMENT 900 800 500 400

    Initial basic feasible solution:

    2 * 900 + 2 * 100 + 6 * 700 + 4 * 0 + 1 * 500 + 0 * 400 = 6700

    Now degeneracy has been removed.

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    4. Arrivals at an STD booth is considered poisson with an average time of 10 minutes

    between them. Length of phone call is assumed exponential with mean 3 minutes. Determine

    a. The probability that a person arriving at the booth will have to wait.

    b. Average Length of queue that form time to time

    c. Average utilization of STD booth.

    Average arrival time = 1 = 10 minutes = 1 hour

    6

    Therefore, = 6 / hour

    Average service time = 1 = 3 minutes = 1 hour

    20

    Therefore, = 20 / hour

    Here, < , so a steady state solution exists.

    a. The probability that a person arriving at the booth will have to wait

    Average waiting time for a person arriving at the booth,

    Wq = = 6

    ( - ) 20 (20 - 6)

    = 6 x 1 hours

    20 14

    = 1.28 minutes

    Therefore, the average waiting time for a person arriving at the booth is 1.28 minutes

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    b. Average length of queue that form time to time

    Expected number of customers in the queue,

    Lq = 2 = 62

    ( - ) 20 (20 - 6)

    = 36

    20 x 14

    = 9 / 70

    Therefore, Lq = 9 / 70

    c. Average utilization of STD booth

    Average time spent in the booth,

    Ls = 1

    -

    = 1

    20 - 6

    = 1 hour

    14

    = 4.28 minutes

    Therefore the average utilization of the STD booth is 4.28 minutes

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    5. Write short notes on:

    i) Dynamic Programming

    ii) Integer Programming

    iii) Pure and Mixed Strategy

    iv) Queue Parameters.

    i. DYNAMIC PROGRAMMING

    Dynamic programming is an optimization approach that transforms a complex problem into a

    sequence of simpler problems. The main characteristic of dynamic programming is the multistage

    nature of the optimization procedure and provides a general framework for analyzing many

    problem types. Within this framework a variety of optimization techniques can be employed to

    solve particular aspects of a more general formulation. Dynamic programming solves problems by

    combining the solutions into sub-problems and can be used when a problem can be divided into

    sub-problems and when these sub-problems are not independent. There are three important

    characteristics of dynamic programming problems explained below.

    Stages

    The essential feature of the dynamic programming approach is the structuring of optimization

    problems into multiple stages, which are solved sequentially one stage at a time. Although each

    one-stage problem is solved as an ordinary optimization problem, its solution helps to define the

    characteristics of the next one-stage problem in the sequence. Often, the stages represent different

    time periods in the problems planning horizon but also, sometimes the stages do not have time

    implications.

    States

    Associated with each stage of the optimization problem are the states of the process. The states

    reflect the information required to fully assess the consequences that the current decision has upon

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    future actions. The specification of the states of the system is perhaps the most critical design

    parameter of the dynamic programming model. There are no set rules for doing this but the

    essential properties that should motivate the selection of states are that the states should convey

    enough information to make future decisions without regard to how the process reached the current

    state and the number of state variables should be small, since the computational effort associated

    with the dynamic programming approach is prohibitively expensive when there are more than two,

    or possibly three, state variables involved in the model formulation.

    Principle of Optimality

    In dynamic programming terminology, each point where decisions are made is usually called a

    stage of the decision-making process. At any stage, knowledge of the intersection currently

    available is needed to be able to make subsequent decisions. Information that summarizes the

    knowledge required about the problem in order to make the current decisions, such as the

    intersection at a particular stage, is called a state of the decision-making process. On these terms,

    the solution to the minimum delay problem involves what is referred to as the principle of

    optimality.

    Any optimal policy has the property that, whatever the current state and decision, the remaining

    decisions must constitute an optimal policy with regard to the state resulting from the current

    decision. To make this principle more concrete, the optimal-value function can be defined in the

    context of the minimum delay problem.

    Vn(Sn) = Optimal value or minimum delay over the current and subsequent stages or intersections,

    given that we are in state Sn in a particular intersection with n stages to go.

    A recursive relationship for computing the optimal value function by recognizing that, at each

    stage, the decision in a particular state is determined simply by choosing the minimum total delay.

    If we number the states at each stage as Sn = 1, which is the bottom intersection, up to Sn = 6 which

    is the top intersection, then

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    Vn (Sn) = Min { tn (Sn) + Vn 1(Sn 1)} , (1)

    subject to:

    Sn 1 = Sn + 1 if we choose up and n even,

    Sn 1 = Sn 1 if we choose down and n odd,

    Sn 1 = Sn otherwise,

    Where, tn (Sn) is the delay time in intersection Sn at stage n.

    ii. INTEGER PROGRAMMING

    An integer programming problem is a mathematical optimization orfeasibility program in which

    some or all of the variables are restricted to be integers. When formulating linearprograms it is

    often found that, certain variables should have been regarded as taking integer values but, for the

    sake of convenience, they are allowed to take fractional values reasoning that the variables were

    likely to be so large that any fractional part could be neglected. While this is acceptable in some

    situations, in many cases it is not, and in such cases we must find a numeric solution in which the

    variables take integer values.

    Problems in which this is the case are called integer programs and the subject of solving such

    programs is called integer programming. Integer programming occurs frequently because many

    decisions are essentially discrete in that one or more options must be chosen from a finite set of

    alternatives. Problems in which some variables can take only integer values and some variables can

    take fractional values are called mixed-integer programs.

    Branch-and-Bound

    Branch-and-bound is essentially a strategy of divide and conquer. The idea is to partition the

    feasible region into more manageable subdivisions and then, if required, to further partition the

    subdivisions. In general, there are a number of ways to divide the feasible region, and as a

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    http://en.wikipedia.org/wiki/Optimization_(mathematics)http://en.wikipedia.org/wiki/Optimization_(mathematics)http://people.brunel.ac.uk/~mastjjb/jeb/or/lp.htmlhttp://en.wikipedia.org/wiki/Optimization_(mathematics)http://en.wikipedia.org/wiki/Optimization_(mathematics)http://people.brunel.ac.uk/~mastjjb/jeb/or/lp.html
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    consequence there are a number of branch-and-bound algorithms. An integer linear program is a

    linear program further constrained by the integrality restrictions. Thus, in a maximization problem,

    the value of the objective function, at the linear-program optimum, will always be an upper bound

    on the optimal integer-programming objective. In addition, any integer feasible point is always a

    lower bound on the optimal linear-program objective value.

    The idea of branch-and-bound is to utilize these observations to systematically subdivide the linear

    programming feasible region and make assessments of the integer-programming problem based

    upon these subdivisions.

    Implicit Enumeration

    A special branch-and-bound procedure can be given for integer programs with only binary

    variables. The algorithm has the advantage that it requires no linear programming solutions. One

    way to solve such problems is complete enumeration. List all possible binary combinations of the

    variables and select the best such point that is feasible. The approach works very well on a small

    problem, where there are only a few potential 01 combinations for the variables.

    In general, though, an n-variable problem contains 2n 01 combinations; for large values of n, the

    exhaustive approach is prohibitive. Instead, one might implicitly consider every binary

    combination, just as every integer point was implicitly considered, but not necessarily evaluated,

    for the general problem via branch-and-bound. Here, we adopt the opposite tactic of always

    maintaining the 01 restrictions, but ignoring the linear inequalities. The idea is to utilize a branch-

    and-bound (or subdivision) process to fix some of the variables at 0 or 1. The variables remaining

    to be specified are called free variables.

    Cutting Planes

    The cutting plane algorithm solves integer programs by modifying linear-programming solutions

    until the integer solution is obtained. It does not partition the feasible region into subdivisions, as

    in branch-and-bound approaches, but instead works with a single linear program, which it refines

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    by adding new constraints. The new constraints successively reduce the feasible region until an

    integer optimal solution is found. In practice, the branch-and-bound procedures almost always

    outperform the cutting-plane algorithm. Nevertheless, the algorithm has been important to the

    evolution of integer programming.

    In addition, even though the algorithm generally is considered to be very inefficient, it has

    provided insights into integer programming that have led to other, more efficient, algorithms.

    iii. PURE STRATEGY AND MIXED STRATEGY

    A Pure Strategy in game theory, also known as Nash equilibrium is a fundamental concept in the

    theory of games and the most widely used method of predicting the outcome of a strategic

    interaction in the social sciences. A game in strategic or normal form consists of the following

    three elements:

    A set of players.

    A set of actions or pure-strategies available to each player.

    A payoff or utility function for each player.

    The payoff functions represent each players preferences over action profiles, where an action

    profile is simply a list of actions, one for each player. A pure strategy Nash equilibrium is an action

    profile with the property that no single player can obtain a higher payoff by deviating unilaterally

    from this profile. This concept can best be understood by looking at some examples.

    Consider first a game involving two players, each of whom has two available actions, called A and

    B. If the players choose different actions, they each get a payoff of 0. If they both choose A, they

    each get 2, and if they both choose B, they each get 1. This coordination game may be represented

    as follows, where player 1 chooses a row, player 2 chooses a column, and the resulting payoffs are

    listed in parentheses, with the first component corresponding to player 1s payoff. The action

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    profile (B,B) is an equilibrium, since a unilateral deviation to A by any one player would result in a

    lower payoff for the deviating player. Similarly, the action profile (A,A) is also an equilibrium.

    Mixed Strategy is another concept in game theory. A game in strategic form does not always have

    a Nash equilibrium in which each player deterministically chooses one of his strategies. However,

    players may instead randomly select from among these pure strategies with certain probabilities.

    Suppose a consumer purchases a license for a software package, agreeing to certain restrictions on

    its use. The consumer has an incentive to violate these rules. The vendor would like to verify that

    the consumer is abiding by the agreement, but doing so requires inspections which are costly. If the

    vendor does inspect and catches the consumer cheating, the vendor can demand a large penalty

    payment for the noncompliance. The standard outcome, defining the reference payoff zero to both

    vendor (player 1) and consumer (player 2), is that the vendor chooses Dont Inspect and the

    consumer chooses to Comply. Without inspection, the consumer prefers to Cheat since that gives a

    positive payoff, with resulting negative payoff to the vendor. The vendor may also decide to

    Inspect and if the consumer complies, inspection leaves the consumers payoff unchanged, while

    the vendor incurs a cost resulting in a negative payoff. If the consumer cheats, however, inspection

    will result in a heavy penalty and still create a certain amount of hassle for player 1.

    In all cases, player 1 would strongly prefer if player 2 complied, but this is outside of player 1s

    control. However, the vendor prefers to inspect if the consumer cheats. If the vendor always

    preferred Dont Inspect, then this would be a dominating strategy and be part of a unique

    equilibrium where the consumer cheats. If any of the players settles on a deterministic choice, like

    Dont Inspect by player 1, the best response of the other player would be unique, here Cheat by

    player 2, to which the original choice would not be a best response. The strategies in Nash

    equilibrium must be best responses to each other, so in this game this fails to hold for any pure

    strategy combination.

    iv. QUEUEING THEORY AND ITS PARAMETERS

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    The main object of Queueing Theory is to develop formulae, expressions, or algorithms

    for performance metrics, such as the average number of entities in a queue, mean time spent in the

    system, resource availability, probability of rejection, and the like. The results from queueing

    theory can directly be used to solve design and capacity planning problems, such as determining

    the number of servers, an optimum queueing discipline, and schedule for service, number

    of queues, system architecture, and the like. Besides making such strategic design decisions,

    queueing theory can also be used for tactical as well as operational designs and controls. The

    queueing parameters can be listed as:

    Arrival pattern/process

    The arrival process or input process to a queueing system is often measured in terms of the average

    number of arrivals per unit of time or by the average time between successive arrivals. Customers

    may arrive for service individually or in groups. Single arrivals are illustrated by customers

    visiting a beautician, students reaching at a library counter, and so on. On the other hand, families

    visiting restaurants, ship discharging cargo at a dock are examples of bulk, or batch, arrivals.

    Customers can also arrive in the system at regular or irregular times, or they might arrive in a

    random way. The queueing models wherein customers arrival times are known with certainty are

    categorized as deterministic models and are easier to handle. On the other hand, a substantialmajority of the queueing models are based on the premise that the customers enter the system

    stochastically, at random points in time. With random arrivals, the number of customers reaching

    the system per unit might be described by a probability distribution. Generally, the queueing

    models are based on the assumption that arrival pattern follows Poisson distribution.

    Speed of service / service mechanism

    In a queueing system, the speed with which service is provided can be expressed in either of two

    ways, as service rate and as service time. The service rate describes the number of customers

    serviced during particular time period. The service time indicates the amount of time needed to

    service a customer. Service rates and times are reciprocals of each other and either of them is

    sufficient to indicate the capacity of the facility. Thus, if a cashier can attend, on average, to 10

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    customers in an hour, the service rate would be expressed as 10 customers per hour and service

    time would be equal to 6 minutes per customer. Generally, however, we consider the service time

    only. If these service times are known exactly, the problem can be handled easily. But, as generally

    happens, if these are different and not known with certainty, we have to consider the distribution of

    the service times in order to analyze the queueing system. Generally, the queueing models are

    based on the assumption based on the assumption that service times are exponentially distributed.

    Queue discipline

    It refers to the manner by which customers are selected for service when a queue has formed. The

    most common discipline that can be observed in everyday life is first come, first served order, or

    first in-first out (FIFO), as it sometimes called some other in common usage are last in-last out

    (LIFO), which is applicable to many inventory systems when there is no obsolescence in stored

    units as it is easier to reach the nearest items which are the last in, and a variety of priority

    schemes, where customers are given priorities upon entering the system, the ones with higher

    priorities to be selected for service ahead of those with lower priorities, regardless of their time of

    arrival to the system.

    Number of servers

    The number of servers or service channels refers to the number of parallel service stations which

    can service customers simultaneously. There can be single servers or multiple server queueing

    system. The two multichannel systems differ in that the first has a single queue, while the second

    allows a queue for each channel. A barber shop with many chairs is an Example of the first type of

    multichannel system, while number of queues before the railway counters is an example of the

    second type of multichannel system.

    System capacity

    In some queueing processes there is a physical limitation to the amount of waiting room, so that

    when the line reaches a certain length, no further customers are allowed to enter, until space

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    becomes available by a service completion. These are referred to as finite queueing situation; that

    is; there is a finite limit to the maximum queue size.

    Size of the population

    The source of customers for a queueing system can be infinite or finite. For example, all people of

    a city or state (and others) could be the potential customers at a super bazaar. The number of

    people being very large, it can be taken to the infinite. On the other hand, there are many situations

    in business and industrial conditions where we cannot consider the population to be infinite-it is

    finite. Thus, the ten machines in the factory requiring repairs and maintenance by the maintenance

    crew would exemplify finite population.

    REFERENCES

    Dynamic Programming, [Online].

    Available at: http://www.cs.berkeley.edu/~vazirani/algorithms/chap6.pdf

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    John, R., A Dynamic Programming, [Online].

    Available at: http://gemini.econ.umd.edu/jrust/research/papers/dp.pdf

    Integer Programming, [Online].

    Available at: http://web.mit.edu/15.053/www/AMP-Chapter-09.pdf

    Wiesemann, W.Integer Programming, [Online].

    Available at: http://www.doc.ic.ac.uk/~br/berc/IPlecture1.pdf

    Mixed Strategy, [Online].

    Available at: http://www.columbia.edu/~rs328/MixedStrategy.pdf

    Nash Equilibrium, [Online].

    Available at: http://www.columbia.edu/~rs328/NashEquilibrium.pdf

    Game Theory, [Online],

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