A firm is starting a large project. Its target capital structure is $25\%$ debt, $20\%$ preferred stock, and the rest with common equity. If the firm doesn$$t want to issue more common stock, and its retained earnings is $$9$ million, what is the most the firm can spend on this project? $($What is the retained earnings breakpoint$)$

a$.$ $$9$ million

b$.$ $$20$ million

c$.$ $$16\mathrm{.}36$ million

d$.$ $$4\mathrm{.}95$ million

e$.$ $$4\mathrm{.}05$ million