Elizabeth and class, which component of cost of capital do you feel had the most significance? Why do you feel management has the most influence over debt? Class, the WACC that should be used in capital budgeting is the firm's marginal, after-tax cost of capital. In firms with 50% debt/50% equity capital structure, the cost of equity will always be greater than or equal to cost of debt. Why does a company need to adjust for taxes when calculating the cost of debt?