2.39 A plane wall of thickness 2L has an internal heat generation that varies according to q = q 0 cos (ax) where q0 is the heat generated per !nit vol! "e at the cener of the wall (x=0) and a is constant. #f $oth sides of the wall are "aintained at a constant te"perat!re of %w derive an expression for the total heat loss fro" the wall per !nit s!rface area.