There are only two firms in an industry with demand curves q1 = 30 - P and q2 = 30 - P. Both have no fixed costs and each has a marginal cost of 10 per unit produced. If they behave as profit-maximizing price takers, each produces 20 units and sells them at a price of 10 so that each firm makes zero economic profits. If they formed a cartel, the profit-maximizing price is

A) 10.
B) 15.
C) 20.
D) 25.

C