Merrion$$s balance sheet shows a total of noncallable $$55$ million long$-$term debt

with a coupon rate of $7\mathrm{.}00\%$ and a yield to maturity of $6\mathrm{.}50\%.$ This debt currently has a market value of $$58$ million. The balance sheet also shows that the company has $10$ million shares of common stock, and the book value of the common equity $($common stock plus retained earnings$)$ is $$65$ million. The current stock price is $$18$ per share; stockholders' required return, rs $,$ is $12\mathrm{.}50\%$; and the firm's tax rate is $21\%.$ The CFO thinks the WACC should be based on market value weights,

but the president thinks book weights are more appropriate. What is the difference between these two WACCs?