how did they calculate the circled number equity number here of 11

Q3 # 10 anale exchange rate Part 3.B XYZ has an expected perpetual EBIT =$4,000. The firm is currently unlevered with 20,000 shares of outstanding, and its cost of equity is 15%. The firm is considering to restructure its funding sources by borrowing $10,000 perpetual debt and buying back some of its shares. The cost of debt is 10% and the firm will pay interest annually. The company's marginal corporate tax rate is 34%. a. What is the value of XYZ before the restructuring? b. What will be XYZ's value after the restructuring? c. What is the cost of equity after the restructuring? Answer Key: Vu = EBIT*(1-Tc) /Ru = 4000*0.66/0.15 = $17,600 V = Vu + D*Tc = $17,600 + $10,000*0.34 = $21,000 D/V1 = 10/21 and E/V1 =(1/21) Re = Ru + (Ru - Rd) *D/E TT-TC) = 0.15 + (0.15-0.10/10/11*0.66 = 0.18, or 18%