Nano Specialist is considering an upgrade project. The estimated cash flows from the upgrade project appear below. What is the project's payback period? Note that year and year 1 cash flows are negative. (Answer in years, round to 2 places) Year 0 cash flow = -80,000 Year 1 cash flow = -37,000 Year 2 cash flow = 23,000 Year 3 cash flow = 40,000 Year 4 cash flow = 27,000 Year 5 cash flow = 33,000 Year 6 cash flow = 37,000 Year 7 cash flow = 31,000