Rollins Corporation's bonds have a 10 percent coupon, paid semiannually, It matures in 13 years, and its current market price is $1,050. The maturity value is $1,000. The firm's marginal tax rate is 40 percent. Which of the following is Rollins' after-tax cost of debt? A. 6.8 percent B. 8.4 percent C. 9.5 percent D.7.2 percent E. 5.6 percent