Assume that a firm uses labor and capital to produce a product. The firm hires labor at a wage rate of $4 per unit and rents capital at $5 per unit. At its current output level, the marginal physical products of labor and capital are 20 and 30 units, respectively. To minimize its cost of production without changing the level of output, the firm should a.) make no changes b.) hire more labor and rent more capital c.) hire less labor and rent more capital d.) hire more labor and rent less capital Hire less labor and rent less capital