Firms in perfect competition

Firms in perfect competition
Paper instructions:
When looking at individual firms in perfect competition, we see that the firm’s supply curve is the upward-sloping part of the firm’s marginal cost curve. However, a firm that is in imperfect competition does not have a supply curve (or at least the marginal cost curve is not the supply curve for a profit-maximizing firm in imperfect competition).
Why is that the case? Explain.


Paper instructions:
When looking at individual firms in perfect competition, we see that the firm’s supply curve is the upward-sloping part of the firm’s marginal cost curve. However, a firm that is in imperfect competition does not have a supply curve (or at least the marginal cost curve is not the supply curve for a profit-maximizing firm in imperfect competition).
Why is that the case? Explain.