An anticipated purchase of equipment for $580,000, with a useful life of 8 years and no residual value, is expected to yield the following annual net incomes and net cash flows: Year Net Income Net Cash Flow 1 $60,000 $110,000 2 50,000 100,000 3 50,000 100,000 4 40,000 90,000 5 40,000 90,000 6 40,000 90,000 7 40,000 90,000 8 40,000 90,000 What is the cash payback period?