(1) According to the annual interest rate for two years, the interest earned after two years of deposit is 80000 * 2.7/100 * 2 * 0.8 = 3456 yuan.

(b) Deposit for one year at the interest rate of one year, and then transfer the after-tax principal and interest together for one year. The interest due in one year is 80000*2.25%*0.8= 1440 yuan, and the interest due in the second year is1440 * 2.25% * 0.8+1440 = 6540 yuan.

The interest paid by method A is 3456-2905.92=550.08 yuan.