Which of the following statements is CORRECT?

a$.$ 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.

b$.$ 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.

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$.$ The WACC for a firm that pays dividends and regularly issues new equity will be greater than the WACC for an otherwise identical company that pays lower dividends and that rarely issues new equity.