what is the internal rate of return on investment?

(Ignore income taxes in this problem) Your Corporation is considering the purchase of a machine that would cost $718,688. It would have a useful life of 15 years. The machine would have no salvage value. The machine would reduce labor and other operating costs by $74,000 per year. What is the internal rate of return on the investment? 4% 3% 6% 8% 5%