The long-run average total cost curve of a firm is flat in the middle because the firm operates at constant returns to scale at those points

A price floor

A) changes the equilibrium price if it is imposed in black markets. B) changes the price and quantity if it is set below the equilibrium price. C) changes the price and quantity if it is set above the equilibrium price. D) does not create a black market if it is set above the equilibrium price. E) changes the price and quantity only if it equals the equilibrium price.

If competing price searchers adjust their own prices on the basis of a close monitoring of their rival's prices,

A) all prices will tend to be the same, which proves prices are not competitive. B) all prices will tend to be the same, which proves sellers are not competing on price. C) each price searcher's demand curve will be indeterminate. D) prices will fluctuate regularly. E) prices will rise when costs increase but will not fall when costs decrease.