A black market develops only when quantity demanded exceeds quantity supplied

Product differentiation allows a firm to charge a higher price because the residual demand curve facing the firm

A) is more elastic than the residual demand curve without product differentiation. B) is less elastic than the residual demand curve without product differentiation. C) is horizontal. D) shifts to the left.

Suppose cars are taxed according to the amount of pollution they emit per gallon of gasoline consumed. We would expect to observe all of the following EXCEPT

A) an increase in quantity demanded of less-polluting automobiles and a reduction in quantity demanded of more-polluting automobiles. B) an increase in quantity demanded of more fuel-efficient cars. C) an increase in production of automobiles that were less polluting. D) an increase in the miles driven.