Need help on an econ M/C Q

An industry has two firms. The demand curve for the industry's output is given by p = 36 - 3q, where q is the total industry output. Each firm has a constant marginal cost equal to 6. Suppose that firms compete in Cournot style (quantity competition). Which of the following statements is correct? Select one: O a. Firm 1's reaction function is 91 = 9 - 0.592- O b. Firm 1's reaction function is q1 = 9 - 92. O c. Firm 1's reaction function is (1 = 5 - 0.592 O d. Firm 1's reaction function is q1 = 5 - 92