please explain how to get answer, use formula

Question 20 ( 1 point) You owe $20,000 in student loans that charge 6.3% annual interest. If you plan to pay back $2,500 at the end of each year, how long will it take to pay off these loans? 13.4 years 11.5 years 9.3 years 10.5 years 12.4 years