X Company currently buys 7,500 units of a part each year from a supplier for $8.10 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 $31,200 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? [Note: 0.03 means 3%, etc.]

A: 0.03

B: 0.04

C: 0.05

D: 0.06

E: 0.07

F: 0.08