A firm can be identified as practicing price discrimination when: a. firms behave as price-takers, whereas consumers react with price-making behavior. b. buyers in a perfectly competitive market are able to influence the prices that firms set. c. consumers engage in comparison shopping to find the lowest advertised price. d. producers pass on differences in costs to those price-conscious consumers willing to buy in bulk. e. producers set different prices for distinct groups of consumers, despite selling identical products to each group.