Scott's Scooters Lid. manufactures three different products, Models A, B, and C. The following per unit data apply: Model A Model B Model C Selling price $110 $90 $50 Direct materials 70 40 20 Direct labor ($40 per hour) 20 20 10 Variable mfg. costs ($60 per machine hour) 6 10 4 Fixed manufacturing costs 10 10 10 Required: a. (2 marks) If there is excess machine capacity, additional units of which model(s) should be produced first to maximize profit? b. (4 marks) If there are a limited number of direct labour hours available and demand exceeds the total direct labour hours available, in what order should the models be produced to maximize total contribution margin