Which of the following statements about cost of capital is correct? Select one: O a. Changing the firm's optimal capital structure will not change its WACC. O b. WACC calculations should be based on before- tax cost for all components Oc. Flotation costs associated with issuing new shares will lead to a decrease in WACC O d. In the corporate tax rate increases, then its average cost of capital will decrease O e. None of the above are correct