Hayden Company is considering the acquisition of a machine that costs $675,000. The machine is expected to have a useful life of 6 years, a negligible residual value, an annual net cash flow of $150,000, and annual operating income of $87,500. What is the estimated cash payback period for the machine?

a. 4 years

b. 3.5 years

c. 4.5 years

d. 5 years