Which of the following statements is correct? a. when calculating the cost of preferred stock, a company needs to adjust for taxes, because preferred stock dividends are deductible by the paying corporation. b. all else equal, an increase in a company's stock price will increase its marginal cost of retained earnings. c. all else equal, an increase in a company's stock price will increase its marginal cost of new common equity. d. if a company's tax rate increases but the ytm on its noncallable bonds remains the same, the after-tax cost of its debt will fall. e. since the money is readily available, the after-tax cost of retained earnings is usually much lower than the after-tax cost of debt.