Arquebus Company is owned and operated by a craftsman who makes replicas of historic firearms for museums, sportsmen and collectors. He is currently producing 40 flintlock muskets per month. Cost data are as follows: Price Variable cost Fixed costs $720 per unit $470 per unit $8,000 per month How much is his margin of safety expressed in units per month? 8 units 6 units 4 units 2 units