Describe 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) Monopoly and (4) Oligopoly. Using the concepts of producer surplus and consumer surplus, describe the long run outcome in each market structure and how producer surplus, consumer surplus and dead weight loss changes.