What is the total of professional courses available at the university? List out all the course id.
professional courses refers to courseLevel = 'Level_500'; course id refers to course.course_id
SELECT COUNT(course_id) FROM course WHERE courseLevel = 'Level_500'
database name:db_id computer_student
course table course Cols: course id dtype integer, course level dtype text, 
person table person Cols: person ID dtype integer, professor dtype integer, student dtype integer, has position dtype text, in phase dtype text, years in program dtype text, 
advisedBy table advisedBy Cols: person id dtype integer, person id dummy dtype integer, 
taughtBy table taughtBy Cols: course ID dtype integer, person ID dtype integer, 
