Among the faculty affiliated professor, how many professors teaches professional or master/undergraduate courses?
faculty affiliated professor refers to professor = 1 and hasPosition = 'Faculty_aff'; professional or master/undergraduate courses refers to courseLevel = 'Level_500'
SELECT COUNT(*) FROM person AS T1 INNER JOIN taughtBy AS T2 ON T1.p_id = T2.p_id INNER JOIN course AS T3 ON T3.course_id = T2.course_id WHERE T1.hasPosition = 'Faculty_aff' AND T1.professor = 1 AND T3.courseLevel = 'Level_500'