Patterson Corp. is considering the purchase of a new piece of equipment, which would have an initial cost of $500,000, a 7-year life, and $150,000 salvage value. The increase in cash flow each year of the equipment's life would be as follows:

Year 1 $ 99,000 Year 2 $ 91,000 Year 3 $ 89,000 Year 4 $ 78,000 Year 5 $ 75,000 Year 6 $ 70,000 Year 7 $ 64,000

What is the payback period?