hello can someone please help me solve this question and teach me step by step this is business finance the solutions are in red i am just having a hard time solving it. could you please show me neatly thanks

Question 5Re=Ru+(RuRd)(D/E)(1Tc) Kuhlmann Corp. has no debt but can borrow at 6.8 percent. The firm's WACC is currently 8.5 percent, and the tax rate is 35 percent. a) What is the company's cost of equity? 8.5% b) If the firm converts to 20 percent debt, what will its cost of equity be? 8.77% c) If the firm converts to 45 percent debt, what will its cost of equity be? 9.4% d) What is the company's WACC in part (b)? In part (c)? 7.88%,7.16%