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.

Use a physical stopwatch to record the length of time it takes to run the program. calculate the difference obtained by calls to the method system. currenttimemillis() just before the start of the algorithm and just after the end of the algorithm. calculate the difference obtained by calls to the method system. currenttimemillis() at the start of the program and at the end of the program so that the elapsed time includes the display of the result. use the value returned by the method system. currenttimemillis() just after the end of the algorithm as the elapsed time.