Consider the following relations for airline flight information: Flights(fno: integer, from: string, to: string, distance: integer, departs: time, arrives: time) Aircraft(aid: integer, name: string, cruisingrange: integer) Certified(eid: integer, aid: integer) Employees(eid: integer, name: string, salary: integer)

Note that (1) the Employees relation describes and other types of employees, (2) every pilot is certified for some aircraft in order being qualified as a pilot, and (3) only pilots are certified to fly.

Write the following queries in relational algebra or tuple relational calculus.

a) Retrieve the eids of pilots certified for some Boeing aircraft.

b) Retrieve the names of pilots certified for some Boeing aircraft.

c) Retrieve the aids of all aircraft that can be used on non-stop flights from Boston to Miami.

d) Identify the flights that can be piloted by every pilot whose salary is more than $110,000.

e) Retrieve the names of pilots who can operate planes with a range greater than 3,500 miles but are not certified on any Boeing aircraft.

f) Retrieve the eids of employees who make the highest salary.

g) Retrieve the eids of employees who are certified for the largest number of aircraft.

h) Retrieve the eids of employees who are certified for exactly four aircraft.

i) Calculate the total amount of salaries paid to employees.

j) Is there a sequence of flights from Jackson to Hannover? Each flight in the sequence is required to depart from the city that is the destination of the previous flight; the first flight must leave Jackson, the last flight must reach Hannover, and there is no restriction on the number of intermediate flights. Your query must determine whether a sequence of flights from Jackson to Hannover exists for ANY input Flights relation instances.