A firm should hire an additional worker if A the minimum wage increases the salary of the worker is not too high C if the worker was referred by a friend if the marginal benefit the firm will receive from hiring the worker is larger than the marginal cost of hiring the workerMovement down along a demand curve could be caused by an increase in the price of a substitute good a decrease in consumer incomes C an increase in consumer's desire or taste for the good a decrease in the price