Which of the following statements about the cost of capital is correct?

Select one:

a.WACC should be calculated based on the marginal costs instead of the historical costs.

b.Weighted average cost of capital calculations should be focused on the before-tax costs.

c.The cost of retained earnings should be zero because there is no direct cost associated with capital raised as retained earnings.

d.A company's target capital structure does not affect its weighted average cost of capital.

e.WACC should be calculated based on the book value instead of the market value.