Booking(agent: String, traveler_ssn: integer, trip_id: integer)

FormedBy(id: integer, location: String, start_date: Date, end_date: Date)

GoesOn(ssn: integer, id: integer)

Leg(location: String, start_date: Date, end_date: Date)

Owns(ssn: integer, passport_number: integer, country: String)

Passport(number: integer, country: String, expiration_date: Date, owner: String)

TravelAgent(name: String, years_experience: integer, phone: String)

Traveller(name: String, ssn: integer, dob: Date)

Trip(id: integer, start_location: String, end_location: String, start_date: Date, end_date: Date)

Find the average number of legs for all trips.

(a) Using Relational Algebra

(b) Create the expression tree of your relational algebra

(c) Using SQL