Say we consider the cost of production of q book cases during the morning production run is given by
(a) C(q) = q2 +q+500 observe that q(t) = 25 t bookcases are produced during the first t hours of a production run for 0<t<=5
To express the production cost in terms of t ,q(t)=25t into C(q) to get
C(q(t))= 25t2+25t+ 500
(b) C (t=3 hours) = 25*3 squared + 25*3 + 500 = $ 6200
(c) C(t=4 hours) = 25*4 squared + 25*4 +500= $ 10400
Now if we take t= 5 hours ,production cost goes beyond $11000 which is the budget for the morning shift.So the time limit is reached after 4 hours.