David currently has $15,000 saved for retirement. For 10 years, he makes no additional contributions to any of his retirement accounts. Then, after this 10 year time period, he begins contributing $750 per month. Assume David can earn 8% on his money, and that interest is compounded monthly.
a. How much will David have saved for retirement after 20 years?
b. Assume the same facts. If David decided to begin saving right away (rather than wait 10 years), how much money would he have to contribute each month to accumulate the same amount of money as in part a above?