A Firm with Two Plants,A and B,has the Following Estimated $$\begin{array} { l } Q _ { d } = 120 - 10 P \\M C _ { A } = 4 + ( 1 / 5 ) Q _ { A } \\M C _ { A } = 6 + ( 1 / 10 ) Q _ { A }\end{array}$$

Multiple Choice

A firm with two plants,A and B,has the following estimated demand and marginal cost functions: $$\begin{array} { l } Q _ { d } = 120 - 10 P \\M C _ { A } = 4 + ( 1 / 5 ) Q _ { A } \\M C _ { A } = 6 + ( 1 / 10 ) Q _ { A }\end{array}$$ What is the profit-maximizing price?

A) $7
B) $8
C) $9
D) $9.50
E) none of the above