Rogers Company is studying a project that would have a ten-year life and would require an $800,000 investment in equipment which has no salvage value. The project would provide net operating income each year based on Sales of $500,000; depreciation expense of $80,000; salary expenses of $120,000; advertising expenses of $80,000l and variable expenses of $100,000. The company's required rate of return is 8%. What is the payback period for this project?