Consider a competitive industry with the following demand curve Q = 50-2p where Q is the number of units demanded and P is the price per unit. The industry consists of identical firms, each with the following cost function: C(q) = 81 + 5q^2, C(0) = 0

- Calculate the marginal cost

- What is the minimum long-run average cost in the industry?

- Calculate the number of firms in the long run.

- What is the long-run equilibrium price? What profits do the firms make?