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 ________.A) 10B) 20C) 690D) 700E) None of the above answers is correct.