Hayden Compony is considering the acquisition of a machine that costs $500,000. The machine is expected to have a useful life of 6 years, a negligibie residual value, an annual net cash inflow of $98,000, and annual operating income of $83,300. The estimated cash payback period for the machine is (round to one decimal place) a. 1.2 years b. 5.1 years c. 60 year d. 7.2 years