Barron Chemical uses a thermoplastic polymer to enhance the appearance of certain RV panels. The initial cost of one process was $120,000 with annual costs of $50,000. Revenues are $85,000 in year 1, increasing by $1000 per year. A salvage value of $24,000 was realized when the process was discontinued after 8 years. What rate of return did the company make on the process?

The rate of return made by the company is %.

Please show work and interpolation