Which of the following is a true statement? Assume that "the company" is profitable, and therefore pays taxes. Select one: a. A company's tax rate affects the firm's cost of debt as well as the cost of equity. b. The higher the firm's tax rate, the lower its effect on the weighted average cost of capital (WACC) c. A company's tax rate affects the firm's cost of debt, but not its cost of equity. d. A company's tax rate affects the firm's cost of cost of equity, but not its cost of debt