instruction: What is the first name of the professor who is teaching CIS-220 and QM-261?
response: 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'