Final answer:
The bailment of Roy's pick-up truck at Sam's Auto Service for an oil change is for the mutual benefit of both Roy (bailor) and the auto service (bailee).
Step-by-step explanation:
A bailment occurs when a person (the bailor) gives possession of property to another (the bailee) for a specific purpose, after which the property is to be returned or otherwise disposed of pursuant to the bailor's directions. In the scenario where Roy leaves his pick-up truck at Sam's Auto Service for an oil change, the bailment is for the parties' mutual benefit. Sam's Auto Service (the bailee) benefits by earning a fee for the service, and Roy (the bailor) benefits by receiving necessary maintenance for his vehicle. This mutual advantage classifies the transaction as a bailment for the mutual benefit of both parties.