Matthew saves $20,000 per month (end of each month) for the next 25 years, after which he retires. During the first five years of retirement, he withdraws $60000 at the start of each month, after which he dies. His son, Sean, inherits the remainder of Matthew's savings. It is further stipulated in Matthew's will that Sean will be paid the money in equal payments at the start of every month, for the next 20 years. Given a fixed interest rate of 9% p.a., calculate the amount of the monthly payments that Sean receives.
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