Problem 1 Consider the following relations containing airline flight information, where the keys are underlined ghts(no: integer, from: string, to: string, distance: integer, departs: time, arrives: time) aircraftlaid: integer, aname: string, crusingrange: integer) certified(eid: integer,aid: integer) employees(eid: integer, ename: string, salary: integer) Note that the employees relation describes pilots and other kinds of employees as well; every pilot is certified for some aircraft (otherwise, he or she would not qualify as a pilot), and only pilots are certified to fly. Note that it is possible that some of the queries below may not be expressible in relational algebra. For such queries, informally explain why they cannot be expressed. Write the following queries in relational algebra. (5 points) a) b) Find the names of pilots certified for some Boeing aircraft. Identify the flights that are piloted by every pilot whose salary is more than 100,000. (5 points) (5 points) c) Find the eid's of employees who make the highest salary