问题如下：
Which of the following statements about the cost of equity is incorrect?
选项：
A. It is the rate of return required by a company’s common shareholders.
B. It uses the market rate instead of coupon rate
C. It also means the cost of retained earning
解释：
B is correct. After-tax cost of debt uses the market rate instead of coupon rate.
After-tax cost of debt uses the market interest rate on new debt. 搞不懂这道题了
