Heidi Company is considering the acquisition of a machine that costs $332,000. The machine is expected to have a useful life of 6 years, a negligible residual value, an annual net cash flow of $131,000, and annual operating income of $82,986. What is the estimated cash payback period for the machine (round to one decimal point)?

a) 2.5 years

b) 4.5 years

c) 4.0 years

d) 4.0 years