corcoran inc. has a capital structure composed of $30$ percent debt, $5$ percent preferred stock. and $65$ percent common equity. Corcorans before tax cost of debt $($kd$)$ is $9\%$ and the cost of preferred stock is $7\%.$ corcoran uses the DCF approach to estimate ks$,$ its current stock price is $30,$ it expects to pay dividend of $2\mathrm{.}10$ in thr next year, and it enjoys consistent growth of $6\%.$ the firms marginal tax rate is $40\%.$ a$.$ calculate firms WACC

b$.$ why is the cost of capital referred to as required rate of return?