How many classes does the professor whose last name is Graztevski teach?
SELECT count(*) FROM employee AS T1 JOIN CLASS AS T2 ON T1.EMP_NUM  =  T2.PROF_NUM WHERE T1.EMP_LNAME  =  'Graztevski'
SELECT count(*) FROM employee AS T1 JOIN CLASS AS T2 ON T1.EMP_NUM  =  T2.PROF_NUM WHERE T1.EMP_LNAME  =  'Graztevski'
[{'count(*)': 3}]