Answer:
Payback period = 5 years 2.23 months
Step-by-step explanation:
Provided information,
Cash outflow = $65,000
Cash inflow for each period = Revenue - Cash cost that is net of depreciation - taxes.
= $21,000 - ($9,600 - $5,700) - $4,560
= $12,540
Therefore, if simple payback period is to be calculated then

That means 5 years and

Simple payback period without any discount rate = 5 years 2.23 months.
Since discount rate not provided it is ignored.
Payback period = 5 years 2.23 months