X Company currently buys 7,500 units of a part each year from a supplier for $8.60 per part, but it is considering making the part instead. In order to make the part, X Company will have to buy equipment that will cost $150,000. The equipment will last for 6 years, at which time it will have zero disposal value. X Company estimates that it will cost $33,990 a year to make all 7,500 units. What is the approximate rate of return if X Company makes the part instead of buying it from the supplier?