Paul takes out a 15-year loan of 250,000 from his bank. The bank charges interest at 4% p.a. compounded half-yearly. During the first 10 years, Paul repays $11,000 at the end of each 6 months. After that period, Paul will repay $X at the end of each year for the remaining 5 years. Which of the following can be used to calculate $X.