Which of the following is not correct? a. Discrimination against workers of a certain race or ethnicity is often in conflict with a firm's desire to maximize profits. b. Signaling theory explains why people with more education are more productive than people with less education and consequently have higher wages. c. The theory of compensating wage differentials explains differences in wages as a result of dangerous working conditions. d. The efficiency wage theory suggests that firms pay higher wages to workers in order to induce workers to be more productive