Answer:
d. 3.5 years
Explanation:
We know that payback period is the estimated length of time it takes cash inflow from a project to recover back the cash outflow.
It is to be noted that the payback period makes use of cash flow and not profit, hence denoted by;
Payback period = Initial cost / Annual net cash inflow
Given that;
Initial cost = $420,000
Annual net cash inflow = $120,000
Therefore,
Payback period = $420,000 / $120,000
Payback period = 3.5 years