4. When marginal revenue is greater than marginal cost, the firm should a. increase the level of output until price is equal to average variable cost. b. stop producing. c. stay at the same level of output. d. reduce the level of output. e. increase the level of output

8. If firms in a perfectly competitive market are making positive economic profits, you would expect firms to ________ the market, causing the ________ curve to shift to the ________. a. enter; demand; right b. enter; demand; left c. enter; market supply; right d. enter; market supply; left e. leave; market supply; left