"Engineering Ecomony" Question

Assume that you have a company and need to evaluate two alternatives, an automatic machine (AM) and a manual machine (MM). Capital investment for these AM and MM are $23,000 and $8,000, respectively. The salvage values for AM and MM are $4,000 and $0, respectively. The AM has a predicted life of 10 years and only one employee will be required to operate this AM at a rate of $12 hourly. Estimated annual costs are $3,500 for the AM. Expected output from AM is 8 tons hourly.

On the other side, we need to have three employees to operate the MM at a rate of $8 hourly for each employee, and estimated useful life of MM is 5 years. Estimated annual costs are $1,500 for the MM. Expected output from MM is 6 tons hourly. If we assume that MARR is 10% yearly for AM and MM, what is the amount of output per year we need to have to choose the AM as the best alternative?