I am absolutely horrible at all things accounting and finance and have been working on this homework for the past week and a half.

I am absolutely horrible at all things accounting and finance and have been working on this homework for the past week and a half. I still cannot figure out these questions and any help would be greatly appreciated. Thanks!Debreu Beverages has an optimal capital structure that is 70% common equity, 20% debt, and 10% preferred stock. Debreu's pretax cost of equity is 9%. Its pretax cost of preferred equity is 7%, and its pretax cost of debt is also 5%. If the corporate tax rate is 35%, what is the weighed average cost of capital?