ECO-4371 Theory of Industrial Structure Solutions Key to Homework #4
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ECO-4371 Theory of Industrial Structure
Solutions Key to Homework #4
Consider a homogenous good market with the following market demand curve:
Q = 100 − p, 0 ≤ p ≤ 100
= 0, p > 100,
where Q = q1 + q2, and p is the price per unit. Two firms produce output at constant marginal cost = $10.
Question 1
Calculate the price (p), and output of each firm (q1, q2) associated to the Cournot - Nash equilibrium.
Answer: q1 = q2 = 30, Q = 60, p = $40, and 1 = 2 = $900
Question 2
Demonstrate that the pair of output q1 = q2 = 10 is not a Cournot - Nash equilibrium. Tip. Let q1 = 10 and show that there exist an output q2 for firm 2, different from 10, at which its profit is larger than that obtained when q1 = q2 = 10. You could use the best response function of firm 2 to find such value of q2 . You can show instead that firm 1 has an incentive to deviate from q1 = q2 = 10.
Question 3
Calculate the output (Q), and the price of each firm (p1, p2) associated to the Bertrand - Nash equilibrium.
Answer: p1 = p2 = $10, Q = 90, and 1 = 2 = 0
Question 4
Demonstrate that the pair of prices p1 = p2 = $15 is not a Bertrand - Nash equilibrium. Tip. Let p1 = $15 and show that there exist a price p2 for firm 2, different from $15, at which its profit is larger than that obtained when p1 = p2 = $15. You could use the best response function of firm 2 to find such value of p2 . You can show instead that firm 1 has an incentive to deviate from p1 = p2 = $15.
In an oligopolistic industry the market demand has a linear form: P = 100 – 2 Q. In that market two firms decide the level of output in a sequential way: first the firm 2, and second the firm 2. They have the same cost structure: Ci(qi) = 50 + 3 qi2, i = 1,2.
Question 5
Write the equation ofthe best response function of firm 2. Answer: q2 = 10 – (1/5) q1 Question 6
Write the set of strategies that correspond to the Perfect Nash Equilibrium
Answer: PNE = {q1 = (200/23) ; q2 = 10 – (1/5) q1}. As a result ofthis equilibrium the output ofthe firms are: q1 = 8.696 and q2 = 8.261.
In an oligopolistic market there are two firms: a leader in price fixing and a follower. The leader fixes the price first, and then the follower takes that price as given and decides the output level. The market demand is Q = 100 – P. The total cost function of the leader (l) is C1(q1) = $10 ql, and the cost function of the follower (2) is C2(q2) = (1/2) (q2)2 .
Question 7
Write the equation ofthe follower´s supply function. Answer: q2 = p
Question 8
Using the result from the previous question, write the equation of the residual demand faced by the leader firm. Answer: q1 = 100 – 2 p
Question 9
Calculate the price and output of each firm that is consistent to the perfect Nash equilibrium Answer: p = $30; q2 = 30 ; and q1 = 40
2022-03-22