Your company is considering the following capital investment in additional plant and equipment. The additional plant and equipment will generate revenues of $1,200,000 per year for as long as you maintain it, increasing by $40,000 each year after the first year. The maintenance cost will start at $350,000 per year and increase by $20,000 each year, after the first year. The plant can be built and will become operational immediately. At the end of eight years, the plant and equipment will be obsolete. Assume that all revenue and maintenance costs occur at the end of the year. The plant and equipment will require an investment of $4,800,000. The discount rate is 9.5 %. Ignore taxation.

Note: the net present value of project is : 147,441 $

how to calculate the payback period of the capital investment?