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 0 and year 1 cash flows are negative. (Answer in years, round to 2 places) Year 0 cash flow = -85,000 Year 1 cash flow = -51,000 Year 2 cash flow = 15,000 Year 3 cash flow = 43,000 Year 4 cash flow = 39,000 Year 5 cash flow = 25,000 Year 6 cash flow = 36,000 Year 7 cash flow = 29,000