Q$.8$ Navarro Corp. has no debt but can borrow at $5\mathrm{.}9$ percent. The firm's WACC is currently

$9\mathrm{.}2$ percent, and the tax rate is $21$ percent.

What is the company's cost of equity?

If the firm converts to $25$ percent debt, what will its cost of equity be$?$

If the firm converts to $50$ percent debt, what will its cost of equity be$?$

What is the company's WACC in part $($b$)?$ In part $($c$)?$