This chapter uses the university database. Its schema:

department(dept_name, building, budget)
instructor(id, name, dept_name, salary)
student(id, name, dept_name, tot_cred)
course(course_id, title, dept_name, credits)
prereq(course_id, prereq_id)
teaches(id, course_id, semester, year)
takes(id, course_id, semester, year, grade)
advisor(s_id, i_id)

In teaches and takes, id is an instructor id and a student id. In advisor, s_id is a student and i_id is an instructor.

1. Write the SQL for the expression department.
2. How many tuples does the expression course return?
3. How many attributes does the schema of takes have?
4. In π title (σ credits = 4 (course)), which operator works first? Give its name.