They can model as one group because the BOMs are all similar. Also, the product transports the same way, and the tires are all relatively the same size. They would need to remodel if they switched from getting tires from the manufacturer instead of a wholesaler because the tires would be coming from different locations and would alter the model. Essentially they all have different product sourcing if they made this decision. The basis for the new product grouping would be a model for each warehouse, including all the tires coming from each one respectively.