Using the Weighted Average Cost of Capital, what is the average cost of capital when: a. the after-tax cost of debt is 8%, the cost of equity is 12% and the ratio of equity to assets is 0.40? b. the after-tax cost of debt is 6%, the cost of equity is 14% and the ratio of equity to assets is 0.70? c. the after-tax cost of debt is 4%, the cost of equity is 8% and the ratio of equity to assets is 0.50?