用方程解
设20000的利率为X%,10000的利率为Y%
20000*(3.24%-Y%)+10000*[3.24%-(3.24%-Y%)]=521.55/95%
Y=0.99%
X=3.24%-0.99%=2.25%
20000元的利率是2.25% 10000元的利率是0.99%
20000*2.25%=450 10000*0.99%=99 450+99=549-(549*5%)=521.55