The Nolan Corporation finds that it is necessary to determine its marginal cost of capital. Nolan's current capital structure calls for $35$ percent debt, $25$ percent preferred stock, and $40$ percent common equity. Initially common equity will be in the form of retained earnings $(K_e)$ and then new common stock $({}_n).$ The costs of the various sources of financing are as follows: debt, $8\mathrm{.}6$ percent; preferred stock, $8$ percent; retained earnings, $14$ percent; and new common stock, $15\mathrm{.}2$ percent.

a$.$ What is the initial weighted average cost of capital? $($Include $$ebt$,$ preferred stock, and common equity in the form of retained earnings, $K_e)($Do not round intermediate calculations. Round the final answer to $2$ decimal places.$)$

Weighted average cost of capital

$\%$

b$.$ If the firm has $$16$ million in retained earnings, at what size of investment will the firm run out of retained earnings? $($Enter the answer in millions.$)$

Capital structure size $(x),$$$,$ million

c$.$ What will the marginal cost of capital be immediately after that point? $($Equity will remain at $40$ percent of the capital structure, but it will all be in the form of new common stock, $K_n)($Do not round intermediate calculations. Round the final answer to $2$ decimal places.$)$

Marginal cost of capital

$\%$

d$.$ The $8\mathrm{.}6$ percent cost of debt referred to above applies only to the first $$28$ million of debt. After that the cost of debt will be $10\mathrm{.}2$ percent. At what size of investment will there be a change in the cost of debt? $($Enter the answer in millions.$)$

Capital structure size $(Z)$ $$,$ million

e$.$ What will the marginal cost of capital be immediately after that point? $($Consider the facts in both parts $c$ and $d.)($Do not round intermediate calculations. Round the final answer to $2$ decimal places.$)$