Heidl Company is considering the acquisition of a machine that costs $441,000. The machine is expected to have a useful life of 6 years, a negligible residual value, an annual net cash inflow of $105,000, and annual operating income of $84,823. The estimated cash payback period for the machine is (round to one decimal point) a. 4.2 years b. 5.5 years c. 5.0 years d. 5.2 years