Jill runs a factory that makes lie detectors in Little Rock, Arkansas. This month, Jill's 34 workers produced 690 machines. Suppose Jill adds one more worker and, as a result, her factory's output increases to 700. Jill's marginal product of labor from the last worker hired equals
◦ 10.
◦ 20.
◦ 690.
◦ 700.
◦ None of these answers is correct.