Consider the University DB with the following relations/tables:
Student (studno, name, hons, tutor, year)
FK: tutor references Staff (lecturer)
Staff (lecturer, roomno)
Enrolled (studno, courseno, labmark, testmark)
FK: studno references Student (studno)
Write queries in relational algebra that return the following:
1) The names of the lecturers who are tutoring a student who had a test mark worse than the lab mark.
2) The names of the lecturers who are tutoring a 3rd year student.
3) The names of the tutors who are tutoring more than one student.
4) The names of the tutors who are tutoring no more than one student.