Final answer:
The transaction between you and Samuel can be categorized as a barter system.
Step-by-step explanation:
The transaction between you and Samuel can be categorized as a barter system. In a barter system, goods or services are exchanged directly without the use of money. In this case, you are offering to make Samuel a delicious roast beef dinner in exchange for him cleaning out your drain line. This type of transaction is common in small communities or between individuals.