The estimated cash payback period for the machine is d. 3.5 years
Calculating the initial investment: $420,000
Calculating the annual net cash flow: $120,000
The cash payback period is the time it takes for the cumulative net cash inflows to equal the initial investment. We can use the following formula:
Cash Payback Period = Initial Investment / Annual Net Cash Flow
Plugging in the values:
Cash Payback Period = $420,000 / $120,000 = 3.5 years
Therefore, it will take approximately 3.5 years for the machine's net cash inflows to cover the initial investment.