4. (5 pts.) Choose the best answer to complete the following sentence and provide a one or two sentence explanation as to why you chose your answer. \"In each sector of a specific- factors economy, profit-maximizing employers will demand labor up to the point where:\" a. the price of the product equals the marginal product of labor times the wage rate. b. the value produced by an additional person-hour equals the price of the product. c. the marginal product of labor equals the wage rate. d. the marginal product of labor times the price of the product equals the wage rate