A borrower wishes to take out a 20 year loan of $350,000 with an interest rate of 7.5%. The borrower will make semi-annual payments of X for 20 years, beginning 6 months after the original loan date. In addition, the borrower will pay a single lump sum payment of $25,000 after the 16th payment. Assuming the loan is paid off exactly with the last semi-annual payment of X, calculate X.