Given the following relational database schema:

Student = (SSN, Name, Major, TotalUnitCompleted)

Course = ( CourseNumber , CourseTitle, NumberOfUnits, RoomNumber, DayTime), where DayTime is of the form MW 1:0-2:00.

Enrollment = (SSN , CourseNumber, Grade)

Use SQL to express the following queries using a minimal number of tables and operations.

a: List the name of every student who did not earn an A in any course

b: List the name of every student who has earned the grade A in every course he or she has taken

c: List the name of every student who is not enrolled in any course that meets in RoomNumber =9