Suppose a firm is operating at an input combination such that MRTSLK < w r. How should the firm adjust its use of labor and capital to reach an optimum input combination? A. the firm should decrease use of both inputs to reach a lower total cost B. the firm should increase its use of capital and decrease its use of labor. C. the firm should adjust the cost of inputs D. the firm should reduce its use of capital and increase its use of labor