Please help me with a,b,c,d . Help me understand and show your work. Thank you

13. Calculating WACC Shadow Corp. has no debt but can borrow at 5.8 percent. The firm's WACC is currently 9.1 percent and the tax rate is 22 percent. a. What is the company's cost of equity? b. If the company converts to 25 percent debt, what will its cost of equity be? c. If the company converts to 50 percent debt, what will its cost of equity be? d. What is the company's WACC in part (b)? In part (c)