Please show the formula on how to calculate the WACC and the optimum debt ratios

Input Data Risk-free rate Market risk premium Unlevered beta Tax rate 4.5% 5.5% 0.8 40.0% Percent Financed with Debt (wa) 0% 10% 20% 30% 40% 50% 60% 70% Before-tax Cost Debt (rd) 6.0% 6.1% 7.0% 8.0% 10.0% 12.5% 15.5% 18.0% 0.8528 8.9 x 0.8 Fill in formulas in the yellow cells to find the optimum capital structure. WACC Debt/Value Ratio (wa) 0% 10% 20% 30% 40% Equity/Value Debt/Equity Ratio (ws) Ratio (wa/ws) 1.0 0.00 0.9 0.11 0.8 0.25 0.7 0.43 0.6 0.67 1.00 0.4 1.50 0.3 2.33 A-T Cost of Debt (ra) 0.000% 7% 15% 26% 40% 60% 90% 140% Levered Beta 0.80 0.85 0.92 1.01 1.12 1.28 1.52 1.92 Cost of Equity 8.900% 9.193% 9.560% 10.031% 10.660% 11.540% 12.860% 15.060% 50% 0.5 60% 70% WACC at optimum debt ratio Optimum debt ratio =