Given the following tables:

students(sid,name,age,gpa)

courses(cid,deptid, description)

professors(ssn,name,address,phone,deptid)

enrollment(sid,cid,section,grade). cid makes reference to the courses table.

teaches(cid,section,ssn). cid, section makes reference to the enrollment table.

Provide SQL instructions for each of the following questions

1. Find the name of the professor with the maximum percentage of students that failed his course.

2. On average what percentage of students fail a course? (total number of students that failed a course / total number of enrolled students).

3. Find a list of courses (sections) where the percentage of students with D or F is greater than average. 1