A firm with a 30% marginal tax rate sells bonds with a $1,000 par value to the public for $968. The investment bank assisting with the bond issuance charges a 3% commission on the purchase price of each bond sold. The bonds mature in 10 years and have an annual coupon rate of 5% (paid semi-annually). What is the after-tax cost of debt for the firm issuing the new bonds? a) 4.07% b) 7.72% c) 9.71% d) 8.60%