5 years ago, Barton Industries issued 25-year noncallable, semiannual bonds with a $900 face value aid a 12% coupon, semiannual payment ($54 payment every 6 months). The bonds currently sell for $845.87. It the firm's marginal tax rate s 40%, what is the firm's after tax cost of debt? Round your answer to 2 decimal places. Do not round intermediate calculations. %