Draw a suitable ER diagram that models the following simplified airline-reservation sys- tem. An airline operates a number of services, each for a direct link from one airport (the origin) to another (the destination). Each service has a distinct code, a fixed departure and arrival time and a capacity (the total number of seats on the aircraft operating the service). Services need not operate daily: some operate only on certain days of the week, others may be seasonal and operate only for specifed periods. Customers have names (first and last), phone numbers and email addresses, as well as distinct customer num- bers. Customers may be booked on specific flights for a particular date. Each booking has a unique booking code and a number, reflecting the number of seats the customer has booked on the flight in question.