6.6 An incumbent firm, Firm 1, faces a potential entrant, Firm 2, with a lower marginal cost. The market demand curve is p = 120 - q1 - q2. Firm 1 has a constant marginal cost of $20, while Firm 2’s is $10.

a. What are the Nash-Cournot equilibrium price, quantities, and profits if the government does not intervene?

b. To block entry, the incumbent appeals to the government to require that the entrant incur extra costs. What happens to the Nash-Cournot equilibrium if the legal requirement causes the marginal cost of the second firm to rise to that of the first firm, $20?

c. Now suppose that the barrier leaves the marginal cost alone but imposes a fixed cost. What is the minimal fixed cost that will prevent entry? (Hint: See Solved Problem 13.5.)