what is the last names of faculties who are members of computer science department?
SELECT T2.Lname FROM DEPARTMENT AS T1 JOIN FACULTY AS T2 ON T1.DNO   =   T3.DNO JOIN MEMBER_OF AS T3 ON T2.FacID   =   T3.FacID WHERE T1.DName   =   "Computer Science"
last names of faculties = T2.Lname; members of computer science department = WHERE T1.DName = 'Computer Science';