Sandhill Industries manufactures and sells three different models of wet-dry shop vacuum cleaners. Although the shop vacs vary in terms of quality and features, all are good sellers. Sandhill is currently operating at full capacity with limited machine time. Per unit sales and production information relevant to each model follows. Economy Standard Deluxe Selling price $33 $55 $110 Variable costs and expenses $18 $22 $52 Machine hours required 0.50 0.80 1.60 N (a1) Calculate unit contribution margin. Economy Standard Deluxe Unit contribution margin $ $ $ eTextbook and Media