Problem
Qian has a loan of 250,000 which has an annual effective interest rate of 5.9%. The loan will be repaid with annual payments for 15 years. The first payment is 10,000. The second payment is 20,000. The third payment is 30,000. The fourth payment is 40,000 . The fifth payment is 50,000. The payments at the end of the sixth through the 15th year are a level amount of Q. Determine the outstanding loan balance right after the 4th payment.