Compute the amount of an annuity. Elke Erbach contributes $5000 to her Individual Retirement Account at the end of each year. a) How much will she accumulate in 20 years if the account earns 8% compounded annually? b) Switch the timing of the payments. Elke learned that she could increase her accumulation if she makes her annual contribution at the beginning of the year rather than at the end. Switch the payments to be made at the beginning of each period and then recalculate the amount of the annuity