Lexington's bonds have 15 years to maturity and a coupon rate of 8%. Interest is paid semi-annually. The bonds sold at par value, but the firm paid flotation costs amounting to 5% of par value. The firm has a marginal tax rate of 21%. What is the firm's after-tax cost of debt for these bonds? 8.0% 8.60% 5.68% 6.32% 6.79%