Question: What are the first names of all students taking accoutning and Computer Information Systems classes?
SQL: SELECT T1.stu_fname FROM student AS T1 JOIN enroll AS T2 ON T1.stu_num  =  T2.stu_num JOIN CLASS AS T3 ON T2.class_code  =  T3.class_code JOIN course AS T4 ON T3.crs_code  =  T4.crs_code JOIN department AS T5 ON T5.dept_code  =  T4.dept_code WHERE T5.dept_name  =  'Accounting' INTERSECT SELECT T1.stu_fname FROM student AS T1 JOIN enroll AS T2 ON T1.stu_num  =  T2.stu_num JOIN CLASS AS T3 ON T2.class_code  =  T3.class_code JOIN course AS T4 ON T3.crs_code  =  T4.crs_code JOIN department AS T5 ON T5.dept_code  =  T4.dept_code WHERE T5.dept_name  =  'Computer Info. Systems'