Q3. Norton's Mufflers manufactures three different product lines: Model X, Model Y, and, Model Z. Considerable market demand exists for all models. The following per unit data apply: Required: a. Calculate the contribution margin per unit. b. Assume that the machine hours are a bottleneck resource, what are the appropriate calculations for decision-making? c. Assume there is excess capacity, which version will be most profitable and Why? d. Assume there is a machine breakdown, which version will be most profitable and