Heidi Company is considering the acquisition of a machine that costs $563,000. The machine is expected to have a useful life of 6 years, a negligible residual value, an annual net cash flow of $129,000, and annual operating income of $89,633. What is the estimated cash payback period for the machine (round to one decimal point)?

5.0 years

6.3 years

6.5 years

4.4 years