Seether Co. wants to issue new 20-year bonds for some much-needed expansion projects. The company currently has 8.4 percent coupon bonds on the market that sell for $910.56, make semiannual payments, and mature in 20 years. What coupon rate (as a APR) should the company set on its new bonds if it wants them to sell at par? (Note: the yield to maturity of the old bonds can be used as the coupon rate for the new bonds.)