Aresearcher studying the effect of price promotions on consumers' expectations makes up two different histories of the store price of a hypothetical brand of laundry detergent for the past year. students in a marketing course are randomly assigned to view one or the other price history on a computer. some students see a steady price, while others see regular promotions that temporarily cut the price. then the students are asked what price they would expect to pay for the detergent.

Which of the following statements is (are) true? i. free entry to a perfectly competitive industry results in the industry's firms earning zero economic profit in the long run, except for the most efficient producers, who may earn economic rent. ii. in a perfectly competitive market, long-run equilibrium is characterized by lmc < p < latc. iii. if a competitive industry is in long-run equilibrium, a decrease in demand causes firms to earn negative profit because the market price will fall below average total cost.