Which of the following is true?

a. if minority and white employees in a skill category are equally productive, the profit motive provides employers with a strong incentive to hire minority employees if they are available at a lower wage.
b. the empirical evidence indicates that the earnings gap between whites and blacks is entirely the result of worker preference.
c. employers who discriminate against blacks and other minorities will have lower costs than rival firms that hire employees strictly on the basis of productivity.
d. after adjusting for factors such as education, experience, and location, the earnings of black men are almost identical to the earnings of white men.

a. if minority and white employees in a skill category are equally productive, the profit motive provides employers with a strong incentive to hire minority employees if they are available at a lower wage.