Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE CLASS ( prof_num VARCHAR )
TABLE: CREATE TABLE employee ( emp_fname VARCHAR, emp_num VARCHAR )

### Question ###
Find the first name of the professor who is teaching two courses with code CIS-220 and QM-261.

### Accurate SQL ###

SELECT T1.emp_fname FROM employee AS T1 JOIN CLASS AS T2 ON T1.emp_num = T2.prof_num WHERE crs_code = 'CIS-220' INTERSECT SELECT T1.emp_fname FROM employee AS T1 JOIN CLASS AS T2 ON T1.emp_num = T2.prof_num WHERE crs_code = 'QM-261'