6. (15 points) Two large firms compete in a market. These two firms produce a homogeneous product and decide their production quantities. Firm 1 decides its quantity first, then Firm 2 decides its quantity given Firm 1's decision. Both firms only have a fixed cost of c (zero marginal cost). The market demand function is linear, and it is D(p) = 1500 - 2p. (a Derive Firm 2's response function by treating y1 as a constant. (b) Solve Firm 1's optimization problem and find both firms' optimal production levels and the equilibrium market price. (c) Now, suppose both firms move simultaneously. Solve both firms' optimal quantity levels and the resulting equilibrium market price. (d) (bonus 3 points) Provide an intuition for the difference in the equilibrium market prices between (b) and (c). For example, why do we have a higher or lower market price in (c)