Mark works full time at a large accounting firm. Mark has been at the firm for four years but has not been given a promotion, even though newer employees have already been promoted. Mark believes he is a victim of labor-market discrimination and threatens to hire a lawyer to sue the company. Which of the following would weaken Mark's case against his employer?
a. Mark is more productive than other newly-hired accountants who were promoted before he was.
b. Mark works more than any other accountant in the firm.
c. Newly hired employees who were promoted before Mark had extensive previous accounting experience.
d. Newly hired employees who were promoted before Mark are more well-liked by other accountants in the firm.