Two $1,000 bonds, redeemable on the same date at par to yield 4.5% have annual coupon rate of "r" and "2r". If the total purchase price of the two bonds is $2,153.52 and the difference of the bond prices is $307.04, find r. The present value of the annuity is an "a", that corresponding to the accumulated value is an "s" and the present value v = (1 + i) ^ (- 1).