Efficiency in a Market Is Achieved When

Multiple Choice

Efficiency in a market is achieved when

A) a social planner intervenes and sets the quantity of output after evaluating buyers' willingness to pay and sellers' costs.
B) the sum of producer surplus and consumer surplus is maximized.
C) all firms are producing the good at the same low cost per unit.
D) no buyer is willing to pay more than the equilibrium price for any unit of the good.