An engineer has a fluctuating future budget for the maintenance of a particular machine. During each of the first 5 years, $1000 per year will be budgeted. During the second 5 years, the annual budget will be $1500 per year. In addition, $3500 will be budgeted for an overhual of the machine at the end of the fourth year, and again at the end of the eighth year. What uniform annual expenditure would be equivalent, if interest is 9% per year?