Problem: Explain why in competitive markets there can be profit or producer surplus in the short run but not the long run. Include the idea of "economic rent" for exceptionally productive inputs. Then imagine a firm with the same cost structure but in each of the four very distinct market structures: (1) Purely Competitive, (2) Monopolistically Competitive, (3) Oligopoly, and (4) Monopoly. Using the concepts of consumer surplus and producer surplus, explain the long run outcome in each market structure and how consumer surplus, producer surplus and dead weight loss changes.