Morgan Jennings, a geography professor, invests $50,000 in a parcel of land that is expected to increase in value by 12 percent per year for the next five years. He will take the proceeds and provide himself with a 10-year annuity. Assuming a 12 percent interest rate, how much will this annuity be?

Why does the exponent (function n) change to a -10 instead of (1.12)^10?