20. Campbell Co. is trying to estimate its weighted average cost of capital (WACC). Which of the following statements is correct? a. The after-tax cost of debt is generally more expensive than the after-tax cost of preferred stock. b. Since retained earnings are readily available, the cost of retained earnings is generally lower than the cost of debt. c. If the company's beta increases, this will increase the cost of equity. d. None of the statements above is correct