Lexington's bonds have 15-year bonds with a coupon rate of 9%. 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?

Group of answer choices

1.60%

6.36%

4.82%

7.61%

9.0%