The price level rises in the short run if a. aggregate demand or aggregate supply shifts left. b. aggregate demand shifts right or aggregate supply shifts left. c. aggregate demand or aggregate supply shifts right. d. aggregate demand shifts left or aggregate supply shifts right.

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.