Given the following relational database schema:

Student = (SSN, Name, Major)

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

Enrollment = (SSN , CourseNumber, Grade)

Express the following queries using AQL statements with minimum number of tables and operations.

a. List the SSN and Name of every student who has no grade in at least one course.

b. List the name of every student who enrolled in at least two courses.

c. List the name of every student who hasnt taken any course.

d. List the SSN and the name of every student who does not have a grade in any course, i.e all her or his grades are null.

e. List the SSN and Name of all students who do not have the grade A in any course.