Take a look at Examples 1 and 3 in the text. Example 1 Total Cost Your cellular phone company ofers you an innovative pricing scheme. When you make a call, the marginal co o the t th minute o the call !ill "e c(t) = 20/(t + 100) $/min. #se a numerical calculation to estimate the cost o a $% minute phone call. Solution &s !e see in the text, the total cost is given "y the de'nite integral, (omputing this integral numerically amounts to "reaking the interval )%, $%* into a large num"er o short intervals, and adding up the costs over these intervals. The smaller the interval, the more accurate the Thus, let us "egin "y deciding on the num"er o divisions !e !ill use, and setting up all the values o t n 1+% The num"er o su"divisions a % The start o the time interval lo!er limit o integration- " $% The end o the time interval upper limit o integration- elta t %./ t c t- c t-0 elta t iemann 2um t starts at a. % &dd elta t 1. We !ill 'll in the t column !it at each step. and continuing in steps o el We !ould like to "e a"le to c length o the columns each ti 5nstead o !orrying a"out sto let t go on or 1%%% or so step you are interested in-, and th !e don7t !ant to sum terms c 2. Test your ormulas "y changi 8o do!n or 9o! 'll in the ormula or c t- 1%%% or so =20/(t+100 steps. !e !ill use =IF(t<$$2 This sets c t- +%; t<1%%- i to ?ero other!ise. 2ee the tu The !idth o each su"interval, given "y " a-;n look at its ormula do not ch ∫ 0 60 20 t +100 dt