Student(snum: integer, sname: string, major: string, level: string, age: integer) Class(name: string, meets at: string, room: string, fid: integer) Enrolled(snum: integer, cname: string) Faculty(fid: integer, fname: string, deptid: integer)

The meaning of these relations is straightforward; for example, Enrolled has one record per student-class pair such that the student is enrolled in the class. Write the following queries in relational algebra NOT SQL. No duplicates should be printed in any of the answers. 1. Find the names of all Juniors (level = JR) who are enrolled in a class taught by I. Teach.

2. Find the age of the oldest student who is either a History major or enrolled in a course taught by I. Teach.

3. Find the names of all classes that either meet in room R128 or have five or more students enrolled.

4. Find the names of all students who are enrolled in two classes that meet at the same time.