Draw an ER diagram for a flight reservation system. This system holds information of airports, airplane types, airplanes, itineraries, flight, and seats reserved for a flight leg. The system handles information such as: 1. An itinerary is defined as from destination A to destination B. It could be one-way, round trip or multi-city trip. For example, New York - Chicago; New York - San Francisco - New York, New York - Chicago - San Francisco - Dallas - Chicago. 2. Each flight is about from departure airport to arrival airport with scheduled times. Each itinerary has one or more flights. 3. Seats are reserved for a flight at a certain amount of fare for customers, and customer's phone number and name should be kept as well. When you book an itinerary, you may just see the total price for the whole itinerary, not the price for each flight. 4. In each airport, what kind of airplane type could land and each airport could land at least one type of airplane. Every airplane has a type. 5. Airline companies purchase airplanes and offer flights. Sometime, a flight is shared by more than one airline companies. 6. Some new airline company may not have airplanes and do not offer flights