Write queries in relational algebra that return the following:

1) The course numbers in which a student had a better exam mark  than lab mark.

2) The names of the lecturers who are tutoring a student who had an  exam mark worse than the lab mark.

3) The names of the lecturers who are tutoring a 3rd year student.

4) The room numbers of the lecturers who are tutoring a 3rd year student.

5) The names of the tutors who are tutoring more than one student

6) The names of the tutors who are tutoring no more than one student