1. Perfectly competitive industries have free entry and exit in the long run. When will firms decide to enter an industry? When will a firm exit an industry?
2. When do economists say that a market is in a long-run competitive equilibrium?
3. Economic rents are returns to scarce inputs above what firms paid for them. When will a firm earn economic rents?
4. Perfectly competitive firms earn zero economic profits in the long run. How can a firm earn zero economic profits and still yield positive economic rents?