The difference between a monopolistically competitive firm in the short run versus the long run is: multiple choice 1 firms only produce at MR = MC in the short run. firms only have P > MC in the long run but not the short run. profit is equal to zero in the long run but not the short run. firms only have P > MC in the short run but not the long run. This is true because: multiple choice 2 firms will be price takers in the long run. the industry can be inefficient in the long run but not in the short run. the industry can be inefficient in the short run but not in the long run. firms will enter as long as profits are positive, given enough time