After graduation, you decide that you can pay $$203\mathrm{.}24$ per month extra on your student loan $($standard monthly payment is $302\mathrm{.}99),$ which has a balance of $$50,000$ and $20$ years of monthly payments remaining.$$ The annual interest rate on the loan is $4\%$ How many years$$early$$will you be able to pay off the loan? Please answer in excel.