Which of the following statements is CORRECT?

a. An increase in the risk-free rate is likely to reduce the marginal costs of both debt and equity.

b. The relevant WACC can change depending on the amount of funds a firm raises during a given year. Moreover, the WACC at each level of funds raised is a weighted average of the marginal costs of each capital component, with the weights based on the firm's target capital structure.

c. The WACC is calculated using a before-tax cost for debt that is equal to the interest rate that must be paid on new debt, along with the after-tax costs for common stock and for preferred stock if it is used.

d. Beta measures market risk, which is generally the most relevant risk measure for a publicly-owned firm that seeks to maximize its intrinsic value. However, this is not true unless all of the firm's stockholders are well diversified.

e. The bond-yield-plus-risk-premium approach to estimating the cost of common equity involves adding a risk premium to the interest rate on the company's own long-term bonds. The size of the risk premium for bonds with different ratings is published daily in The Wall Street Journal or is available online.