Final answer:
In this instance, Broker Bill is acting as the principal broker.
Step-by-step explanation:
In this instance, Broker Bill is acting as the principal broker. As the principal broker, Bill is responsible for overseeing and managing the real estate agents working under him, such as Agent Bob and Agent Sue. In this scenario, Bob obtained the owner listing to lease a building, while Sue located a tenant for Bob's listing. As the principal broker, Bill is entitled to a commission from the transaction.