DeMarzo Enterprises currently has one bond issue outstanding. The bonds are unsecured debentures that mature 15 years from now. The outstanding bonds have a $1000 face value, an annual coupon rate of 6.4%, and coupons are paid annually. The price of the bonds today is 842.45. DeMarzo now wants to sell new 15-year unsecured debentures. DeMarzo's CFO wants to be sure the new bonds will sell at their par value of $1000 on the day they are issued. What coupon rate should the CFO set on the new issue? Assume that for both bond issues the next coupon payment will occur one year from now