Dave takes out a 22-year mortgage of 260000 dollars for his new house. Dave gets an interest rate of 16.8 percent compounded monthly. He agrees to make equal monthly payments, the first coming in one month. After making the 69th payment, Dave wants to buy a boat, so he wants to refinance his house to reduce his monthly payment by 500 dollars, and to get a better interest rate. In particular, he negotiates a new rate of 7.2 percent compounded monthly, and agrees to make equal monthly payments (each 500 dollars less than his original payments) for as long as necessary, followed by a single smaller payment. How large will Dave's final loan payment be?