Please provide steps

1) Annual investments are being made so that S20,000 will be accumulated at the end of 10 years. The interest rate on these investments is initially expected to be 4 percent compounded annually. After 4 years, the rate of interest is unexpectedly increased to 5 percent, so that payments for the remaining 6 years can be reduced What amounts should be invested annually for the first 4 years and what sums for the last 6