Write the following queries in relational algebra, using the university
schema.
a. Find the names of all students who have taken at least one Comp. Sci.
course.
b. Find the IDs and names of all students who have not taken any course
offering before Spring 2009.
c. For each department, find the maximum salary of instructors in that
department. You may assume that every department has at least one
instructor.
d. Find the lowest, across all departments, of the per-department maximum
salary computed by the preceding query.
