$FV=A*{\displaystyle \underset{t=0}{\overset{(n-1)}{}}}(1+r{)}^t=A*\frac{(1+r{)}^n-1}{(1+r)-1}=A*\frac{(1+r{)}^n-1}{r},$F$).$ Now assume you did not increase your monthly mortgage payments back in year $2$ of the mortgage, and instead opened an ordinary annuity account that pays $3\%$ annual interest and you made monthly payments there of $$500$ for $20$ years. Use equation $2\mathrm{.}13,$ page $28,$ to determine what that annuity asset is worth now after $20$ years of deposits.