You are the manager of a firm that produces output in two plants. The demand for your firm's product is P = 78 - 15Q, where Q = Q1 + Q2. The marginal cost associated with producing in the two plants are MC1 = 3Q1 and MC2 = 2Q2. What price should be charged in order to maximize revenues?
A. $39
B. $47
C. $52
D. $56