The management of Cooper Corporation is considering the purchase of a new machine costing $420,000. The company's desired rate of return is 10%. The present value factors for $1 at compound interest of 10% for 1 through 5 years are 0. 909, 0. 826, 0. 751, 0. 683, 0. 621, respectively. In addition to this information, use the following data in determining the acceptability in this situation:

Year Income from Operations Net Cash Flow
1 $100,000 $180,000
2 40,000 120,000
3 20,000 100,000
4 10,000 90,000
5 10,000 90,000

The cash payback period for this investment is: ___________