Which of the following statements best expresses a firm’s profit-maximizing decision rule? a. If marginal revenue is greater than marginal cost, the firm should increase its output. b. If marginal revenue is less than marginal cost, the firm should shut down in the short run. c. If marginal revenue equals marginal cost, the firm should produce exactly one more unit of output. d. All of the above are correct.

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends > a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?