A firm is currently buying a part at a cost of $12 each. It is considering buying a machine that will produce the part at a variable cost of $8. Each unit of input produces the part plus a by-product, which is sold for $1. The machine will cost $40,000 and will have a useful life of 5 years. The firm requires an 8% return. What annual volume is necessary to justify making the investment? Ignore income taxes. Round to the nearest unit.