Process Unit X costs $10,000 more than Unit Y. However, in use, Unit X averages 0.08 hours of maintenance labor per day versus Unit Y with an average of 0.14 hours of maintenance labor per day. Both Units X and Y have a 15-year useful life. Unit Y has a salvage value that is $2,000 less than Unit X. Maintenance costs per hour are $85.00 which is fully burdened including consumables and related tool costs, etc. It is anticipated that both Unit X and Unit Y will be utilized intermittently throughout the year. Given that all other factors (safety, quality, thru-put, etc.) are equal, beyond how many days of use is Unit X preferred over Unit Y