Which one of the following statements is correct? Dividends on preferred stock are tax deductible and therefore a firm's cost of preferred stock should be considered on an after-tax basis. A firm should accept all projects for which IRR exceeds WACC, regardless of project risk. A lower risk project should be evaluated using a discount rate that is lower than the firm's overall cost of capital. The most appropriate weights to use in the WACC are calculated using the book values of debt, common stock, and preferred stock. A firm's WACC is not affected by changes in corporate tax rates