Rapidan Tool Company makes three types of wrenches-small, medium, and large. Medium wrench Unit selling price Unit variable cost Small wrench $130 $140 $40 Large wrench $160 $40 $40 Unit contribution margin Heat treatment hours $90 $100 $120 1 hour per unit 4 hours 8 hours Based upon the above information, which of the following statements is true, considering the production constraint of heat treatment hours per unit? The large wrench is the most profitable. The medium wrench is the most profitable. The small wrench is the least profitable. The large wrench is the least profitable