Let C(q) represent the cost, R(q) the revenue, and π(q) the total profit, in dollars, of producing q items.

Question

a) If C′(67) = 65 and R′(67) = 86, approximately how much profit is earned by item number 68?
b) If C′(149) = 120 and R′(149) = 98, approximately how much profit is earned by item number 150?

Answer 1

marginal profit = R'(x)-C'(x)
a).
Profit for item 68
= π'(67)
= R'(67)-C'(67)
= 86-65
= $21

I'll let you try b).