QUESTION $4$

Consider a database of flight departures and airplanes, with the following schema:

Departure$($departureID$,$ airplaneID,destination,departureTime,bookedSeats$)$

Airplane$($airplaneID$,$modelID,fabricationYear$)$

Model$($ModelID$,$name,capacity$)$

Primary keys are underlined. Write SQL queries to answer the following:

$($a$)$ Write an SQL query that lists the airplaneID of all airplanes made before $1960.$

$(5$ marks$)$

$($b$)$ Write an SQL query that lists the departureID for all departures bounded for destinations starting with the letter $"D".$

$(6$ marks$)$

$($c$)$ Write an SQL query that lists the average capacity of airplanes fabricated $1970$ or later.

$(7$ marks$)$

$($d$)$ Write an SQL query that lists the departureID for every overbooked departure $($i$.$e$.$ where the number of bookings exceed the capacity of the plane$).$