Set up an absolute matching strategy for the payment of $56,000 after one year, $62,500 after two years, $75,600 after three years, and $80,000 after four years if the annual coupon for the one year bond is 2%, for the two year bond 5%, the three year bond 3%, and the four year bond 4%. The effective annual rate of interest is 6%. Find the yield rate of this investment strategy.