Suppose the U.S. Treasury offers to sell you a bond for $660. No payments will be made until the bond matures 10 years from now, at which time it will be redeemed for $1,000. What interest rate would you earn if you bought this bond at the offer price?

a. 6.40% b. 3.85% c. 4.24% d. 4.73% e. 15.15%