What is the internal rate of return?

[geol19]

mechanical engineer with an entrepreneurial spirit started a tire business to take advantage of a state law that punishes all waste tires in landfills. The cost of grinding was 220 000. She spent 15000 for obtaining a plant of 460 volts for the site and other 76000 on site preparation. Through contracts with vendors of tires, she paid $ 2 per tire and drove an average of 120,000 tires per year for 5 years. The annual operating costs for labor, energy, repairs, etc.went up to $ 1.05 per tire. She also sold some of the waste tire installers for use in septic drain fields. The company earned $ 12,000 net per annum. After 5 years, she sold the equipment for $ 92,000. What annual rate of return did she get in her business?