Which of the following statements is correct? a. When calculating the cost of debt, a company needs to adjust for taxes, because interest payments are deductible by the paying corporation b. When calculating the cost of the preferred stock, companies must adjust for taxes, because dividends paid on preferred stock are deductible by the paying corporation c. Because of tax effects, an increase in the risk-free rate will have a greater effect on the after-tax cost of debt than on the cost of common stock d. If a company's beta increases, this will increase the cost of equity used to calculate the WACC, but only if the company does not have enough retained earnings to take care of its equity financing and hence needs to issue new stock