Answer:
a. cost of debt
Explanation:
The formula to compute the weighted average cost of capital is shown below:
= Weightage of debt × cost of debt × ( 1- tax rate) + (Weightage of preferred stock) × (cost of preferred stock) + (Weightage of common stock) × (cost of common stock)
Since the payment for the dividend is not entitled to a tax deduction but the payment for interest is entitled to a tax deduction. And, the after-tax is considered for the cost of debt and the same is shown in the formula above