Answer the questions please

The Cypress Company's cost of retained earnings (Rs or Is) is currently 15%, their cost of external equity (Re or Ie) is 18%, and their bond's carry a coupon rate of 10% and a current yield to maturity of 9%. Their average tax rate is 30 percent. Their book value and market value are the same. Using following balance sheet: A) Calculate the company's after-tax weighted average cost of capital using retain earnings: B) Calculate the company's after-tax weighted average cost of capital if additional equity holders must be obtained