Shelby Company produces three products: product X, product Y, and product Z. Data concerning the three products follow (per unit): Product X Product Y Product Z Selling price $ 70 $ 50 $ 60 Variable expenses: Direct materials 21.00 15.00 4.20 Labor and overhead 21.00 22.50 37.80 Total variable expenses 42.00 37.50 42.00 Contribution margin $ 28.00 $ 12.50 $18.00 Contribution margin ratio 40 % 25 % 30 % Demand for the company