Suppose for the situation described in Exercise 65, it costs the fishery C(t) = 50 + 1.2t hundred dollars to maintain and monitor the pond for t weeks after the fish are released, and that each fish harvested after t weeks can be sold for $2.75 per pound.

a. If all fish that remain alive in the pond after t weeks are harvested, express the profit obtained by the fishery as a function of t.

b. When should the fish be harvested to maximize profit? What is the maximum profit?