(7) Suppose that a revenue function is given as R(x) = 3r³ +36r²+10r and a cost function is given as C(r) = 4r³ +15² +82x-500, where r is the number of

items. (a) Find the profit function P(r) in this situation. (b) What production level a maximizes profit? (c) What is the maximum profit?