Which of the following is not correct?

a. Some economists believe that business owners who emphasize profit maximization will hire the most productive workers regardless of the personal characteristics of the worker; hence, these firms will drive discriminating firms out of business.

b. Two economists found that women were less likely to participate in an experiment where they were paid based on math skills but more likely to participate when they were paid based on reading skills; men were more likely to participate when they were paid based on math skills and less likely to participate when they were paid based on reading skills.

c. Economists found that the prices of older baseball cards were about 10 percent lower when the player was black rather than white.

d. Two economists found that employers in Boston and Chicago were about 50 percent more likely to interview job applicants named Emily and Greg than those named Lakisha and Jamal.