Rusty Nails, Inc. has an optimal capital structure that is 70% common stock, 10% preferred stock, and 20% debt. Rusty's cost of equity is 9%. Its cost of preferred equity is 7%, and its before tax cost of debt is 5%. If Rusty's tax rate is 21%, what is the WACC? O 8% 7.79% 5.2% 8.74%