A machine shop has three options for a new milling machine. Machine Orpheus has a fixed cost of $5,000, Machine Rex has a fixed cost of $15,000, and the Zulu Machine has a fixed cost of $25,000. The per-unit cost to operate the equipment is $12 for Orpheus, $8 for Rex, and $6 for Zulu. For what range is the total cost of a Zulu machine lowest? a. 3,333 units and higher b. 5,000 units and higher c. 2,500 units and higher d. It is always less expensive to have a Zulu