Hayden Company is considering the acquisition of a machine that costs $406,000. The machine is expected to have a useful life of six years, a negligible residual value, an annual net cash flow of $96,000, and annual operating income of $81,600. What is the estimated cash payback period for the machine (round to one decimal points)? a.6.2 years b.5.0 years c.4.2 years d.1.2 years