5.12. Consider the AIRLINE relational database schema shown in Figure 5.8, which describes a database for airline flight information. Each FLIGHT is identified by a Flight_number, and consists of one or more FLIGHT_LEGs with Leg_numbers 1, 2, 3, and so on. Each FLIGHT_LEG has scheduled arrival and departure times, airports, and one or more LEG INSTANCEs- one for each Date on which the flight travels. FAREs are kept for each FLIGHT. For each FLIGHT LEG instance, SEAT_RESERVATIONs are kept, as are the AIRPLANE used on the leg and the actual arrival and departure times and airports. An AIRPLANE is identified by an Airplane_id and is of a particu- lar AIRPLANE_TYPE. CAN LAND relates AIRPLANE TYPEs to the AIRPORTs at which they can land. An AIRPORT is identified by an Airport_code. Con- sider an update for the AIRLINE database to enter a reservation on a particu- lar flight or flight leg on a given date. a. Give the operations for this update b. What types of constraints would you expect to check? c. Which of these constraints are key, entity integrity, and referential integ- rity constraints, and which are not? d. Specify all the referential integrity constraints that hold on the schema shown in Figure 5.8