I have a schema

I want these SQL queries

1. Find the top 4 instructors whose courses have the maximum enrollment in all of their courses combined.

Output columns: InstructorName, TotalEnrollment

Sort by: TotalEnrollment in descending order

2. List all the courses offered by the departments Comp. Sci. and History. Output should not contain any duplicates.

Output columns: DepartmentName, CourseID

Sort by: CourseID in ascending order.

3. List all the courses that have prerequisites offered by a different department.

Output columns: Course_id, Course_department, Prereq_id, Prereq_department

Sort by: Course_id in ascending order