Shadow Corp. has no debt but can borrow at $6\mathrm{.}7$ percent. The firm$$s WACC is currently $8\mathrm{.}5$ percent, and the tax rate is $21$ percent.

a$.$ What is the firm$$s cost of equity?

b$.$ If the firm converts to $20$ percent debt, what will its cost of equity be$?$

c$.$ If the firm converts to $40$ percent debt, what will its cost of equity be$?$

d$-1.$ If the firm converts to $20$ percent debt, what will the company's WACC be$?$

d$-2.$ If the firm converts to $40$ percent debt, what will the company's WACC be$?$