The docking station industry is perfectly competitive. Each firm producing the stations has long-run cost curve given by C = 400 + 20q + q2. (You may assume this is both the short-run and the long-run cost curve.) The market demand is given by Q = 3000 - 25p. The long-run equilibrium number of firms is ....?

a. 75

b. 45

c. 20

d. 60