How many course credits are each of those worth?
SELECT CRS_CREDIT FROM course WHERE CRS_CODE in  ( SELECT T1.CRS_CODE FROM course AS T1 JOIN department AS T2 ON T1.dept_code   =   T2.dept_code WHERE T2.dept_name  =  "Computer Info. Systems" ) 
course credits refers to CRS_CREDIT; worth refers to the value of CRS_CREDIT; those refers to courses; in the department specified by dept_name = 'Computer Info. Systems';