Which of the following statements is correct? a. The after-tax cost of debt that should be used as the component cost when calculating the WACC is the average after-tax cost of all of the firm's outstanding debt. b. The cost of equity is generally harder to measure than the cost of debt because there is no stated, contractual cost number on which to base the cost of equity. c. The cost of capital used to evaluate a project should be the cost of the specific type of financing used to fund that project, i.e., it is the after-tax cost of debt, if debt is to be used to finance the project, or the cost of equity, if the project will be financed with equity. d. The bond-yield-plus-risk-premium approach is the most sophisticated and objective method for estimating a firm's cost of equity capital