4 years ago in order to accumulate a good down payment for your first home, you deposited $20,000 in an investment that earned you 0.5% per month. You aim to accumulate a down payment of $50,000, and you will need it in exactly 3 years. You realize you won't have enough money unless you add a good amount today. You expect an interest rate of 5% per year for the next 3 years.

The amount you have already accumulated obviously remains invested and will earn this new rate of 5% per year for the next 3 years? How much do you need to deposit today to reach your goal?