Suppose that the schemas of $6$ relations are as follows. department $($dept$\_$name char$(50),$ building char$(50),$ budget integer$)$ course $($course$\_$id char$(20),$ title char$(20),$ dept$\_$name char$(50),$ credits integer$)$ section $($course$\_$id char$(20),$ sec$\_$id char$(20),$ semester char$(20),$ year integer, building char$(20))$ instructor $($id char$(20),$ name char$(20),$ dept$\_$name char$(20),$ salary double$)$ student $($id char$(20),$ name char$(20),$ dept$\_$name char$(20),$ tot$\_$cred integer$)$ takes $($id char$(20),$ course$\_$id char$(20),$ sec$\_$id char$(20),$ semester char$(20),$ year integer, grade integer$)$