2. Let the following be the role hierarchy relationships. Note that (ri,Tj) means role ri is senior to role rj. Let each role be assigned to exactly one unique user (user u is assigned to role r) RII { (ri,T2), (ri, rs), (r2, ra), (T2.rs), (r3,rs), (r6 ,T3), (r6,T7), (T7.rs)} (a) Draw the role hierarchy. (Hasse diagram). . . (b) Determine authorized_ users(r3) and authorized users(r