Classes:

New Vehicles

Recreational vehicles/Travel trailers

Trade-in vehicle

Options

Customer

Salesperson

Purchase/invoice

Assumption, recreational vehicles and travel trailers are looked at as a single sale unit or are treated as "vehicle" for the purpose of this case. Some students will argue that these have different attributes and should be subclasses of new vehicle. Although trade-in vehicle is considered as a separate class, since it has the same attributes as "new vehicle" this could also be considered a subclass of new vehicle