Design the object-oriented model for an elevator (lift) system in a multi-floor building that may have **multiple elevators**. The system should support: - **External requests**: people on each floor can press Up/Down call buttons. - **Internal requests**: passengers inside the elevator can select a destination floor. - An elevator can move up/down, open/close doors, and stop at requested floors. - A **scheduler/controller** decides which elevator should handle which requests (especially when there are multiple elevators). **Tasks** 1. Identify and describe the **main classes**, their responsibilities, and relationships. Examples might include: `Elevator`, `ElevatorController`, `Floor`, `Request`, `Button`, etc. 2. Explain how the system handles **request flow** end-to-end: - A user presses an Up/Down button on a floor. - An elevator is assigned and moves to that floor. - The user selects a destination floor inside the elevator. - The elevator services multiple requests while moving. 3. Propose a **scheduling strategy** (algorithm) for choosing which elevator should handle new requests (at a high level, not full code). Discuss how it works in typical scenarios (e.g., many people going up in rush hour). 4. Discuss how your design can handle **edge cases and extensions**, such as: - Elevators going into maintenance mode. - Overload (too many people inside). - Emergency stop or fire mode. - Adding more elevators or floors in the future. You may use UML-style notation or plain text descriptions for classes and interactions.