long-run profit maximization -  

• marginal costs change now that firm can adjust more inputs in long run
• economic profit made as long as marginal cost (equal to price) above the average total cost
• zero economic profit - firm earning a normal (competitive) return on investment
  • normal return - equal to investing elsewhere (whether in capital or other industry)
• high profit >> other firms enter market (assuming free entry) >> increases output >> drives down prices >> reduces profit

      long-run competitive equilibrium - when no exit/entry  

• firms earning zero economic profit >> no incentive to enter or exit
• all firms must be maximizing profit
• quantity supplied by industry equal to quantity demanded by consumers
• patents act as opportunity cost for firms that have it
  • can be sold or kept to produce a positive profit

economic rent - willingness of firms to pay for an input less than the minimum amount  

• some firms have natural advantages over others
  • land might be beneficial to shipping
  • materials might be more readily accessible
• gives firm an edge >> other firms willing to pay for that edge >> economic rent

long-run supply curve - cannot just sum curves like w/ short-run  

• in long-run, markets and enter/exit, so no way to tell how many total firms are in the market
• constant-cost industry - horizontal long-run supply curve, very elastic
• unlike short-run, where 1 input held constant, both inputs can vary in the long-run
  • use MRTS to relate wages/rent to marginal labor/capital functions (in terms of Q)
  • C(Q) = wL(Q) + rK(Q)
• curve generally wider than short-run curve
  • MC-MR intersection located farther to the right