1. Market demand in a perfectly competitive market is Qd = 2220 5p. Each identical firm in this market has a supply curve qs = 6p. If equilibrium market price is currently $12, how many firms are there in this market?
2. Suppose the total cost of producing Q units of a good is 3Q.
   1. What is the marginal cost of production? What is the average cost?
   2. What are the marginal and average costs if the total cost of producing Q units of a good is 3Q2?
   3. Suppose there are $10 of fixed costs. What are the marginal and average costs if the total cost of producing Q units of a good is 3Q2 + 10?
   4. What happens to the total quantity produced by a firm if its fixed costs increase, assuming the firm stays in business?