Heidi Company is considering the acquisition of a machine that costs $472,500. The machine is expected to have a useful life of six years, a negligible residual value, an annual net cash flow of $94,500, and annual operating income of $63,000. What is the estimated cash payback period for the machine (round to one decimal point)? Oa 15 yvan Ob 10 years Oc 75 years Od so year