Artisan Works is owned and operated by a craftsman who makes replicas of historic firearms for museurns, sportsmen, and collectors. The data are as follows: Sales price per unit $800 Variable cost per unit 470 Fored costs per month 10,890 Artisan expects to well 40 units per month, what is his margin of safety expressed in units per month? A T3 units OB. 5 units C. 7 units D. 40 units