The cost of debt that is relevant when companies are evaluating new investment projects is the marginal cost of the new debt to be raised to finance the new project.

Consider the case of Purple Lemon Shipbuilders Inc. (Purple Lemon):

Purple Lemon Shipbuilders Inc. is considering issuing a new 15-year debt issue that would pay an annual coupon payment of $85. Each bond in the issue would carry a $1,000 par value and would be expected to be sold for a price equal to its par value.

Purple Lemons CFO has pointed out that the firm would incur a flotation cost of 1% when initially issuing the bond issue. Remember, the flotation costs will besubtracted from the proceeds the firm will receive after issuing its new bonds. The firms marginal federal-plus-state tax rate is 40%.

To see the effect of flotation costs on Purple Lemons after-tax cost of debt (generic), calculate the after-tax cost of the firms debt issue with and without its flotation costs, and select the correct after-tax costs (in percentage form):

After-tax cost of debt without flotation cost:
After-tax cost of debt with flotation cost:

This is the cost of debt, and it is different from the average cost of capital raised in the past.