27. A retired couple plans to supplement their Social Security with interest earned by a $120,000 retirement fund. a. If the fund compounds interest monthly at an annual rate of 6%, which the couple takes out and spends each month, how much interest is generated each month? b. Suppose the annual interest rate suddenly drops to 3%. What is the resulting interest payment each month? c. Estimate the annual interest rate needed to generate $900 each month in interest