Q6. In the long-run, a firm operating under perfect competition will:

A)   produce a quantity where marginal revenue is less than marginal cost.

B)   face a vertical demand curve.

C)   generate zero economic profit.

Q7. A firm operating under perfect competition will experience economic losses when which of the following conditions exists?

A)   Marginal cost is less than average total cost.

B)   Market price is less than average total cost.

C)   Marginal revenue is greater than average total cost.

Q8. Assume that a perfectly competitive firm produces 10 units of a good and sells them each for a price (P) equal to $15. If the marginal cost (MC) of the 10th unit is $15 and the average total cost (ATC) is $13, economic profit for the firm is closest to:

A)   $20.

B)   $0.

C)   $120.

Q9. A profit maximizing firm will expand output as long as marginal revenue is:
   

A)   greater than average fixed cost.

B)   greater than marginal cost.

C)   less than marginal cost.

Q10. A competitive firm will tend to expand its output as long as:
   

A)   its marginal revenue is greater than the market price.

B)   its marginal revenue is positive.

C)   the market price is greater than the marginal cost.

[此贴子已经被作者于2009-1-6 13:48:19编辑过]

答案和详解如下：

Q6. In the long-run, a firm operating under perfect competition will:

A)   produce a quantity where marginal revenue is less than marginal cost.

B)   face a vertical demand curve.

C)   generate zero economic profit.

Correct answer is C)

A firm operating under conditions of perfect competition will generate zero economic profit in the long run. Firms may generate economic profits in the short run, but due to the lack of entry barriers, new competitors will enter the market and prices will adjust downward until economic profits become zero.

Q7. A firm operating under perfect competition will experience economic losses when which of the following conditions exists?

A)   Marginal cost is less than average total cost.

B)   Market price is less than average total cost.

C)   Marginal revenue is greater than average total cost.

Correct answer is B)         

Under perfect competition, a firm will experience economic losses when its selling price is less than average total cost.

Q8. Assume that a perfectly competitive firm produces 10 units of a good and sells them each for a price (P) equal to $15. If the marginal cost (MC) of the 10th unit is $15 and the average total cost (ATC) is $13, economic profit for the firm is closest to:

A)   $20.

B)   $0.

C)   $120.

Correct answer is A)

When MR = MC = P, economic profit equals TR – TC. In this case, TR = $150 = 10 × $15 and TC = $130 = 10 × ATC = 10 × $13. So, economic profit is $20 = $150 − $130.

Q9. A profit maximizing firm will expand output as long as marginal revenue is:

A)   greater than average fixed cost.

B)   greater than marginal cost.

C)   less than marginal cost.

Correct answer is B)

A purely competitive firm will tend to expand its output so long as the market price (marginal revenue) is greater than marginal cost. In the short term and long term, profit is maximized when P = MC.

Q10. A competitive firm will tend to expand its output as long as:

A)   its marginal revenue is greater than the market price.

B)   its marginal revenue is positive.

C)   the market price is greater than the marginal cost.

Correct answer is C)

A competitive firm faces a flat demand curve. This means the price is constant and the marginal revenue line is flat. A firm will continue to produce as long as MR > MC, so the competitive firm will produce as long as P > MC. It will stop when MC = MR = P.