8. On Laulima, go to the tool [Roster (note: you have to scroll and scroll to make the whole list visible bad user interface!). Viewing the roster as a relational database: (a) Which of the six attribute_ Picture, Name, User ID, Role, Groups, Connected could serve as primary keys to the relation?5 points] Replace this text with your answer. (b) Are there any attributes which can form a composite key, which by themselves cannot be primary keys? 5 points] Replace this text with your answer. Variation on 9.2#11]. What do you get when you apply the selection condition Groups- "Ungrouped" to the database? [5 points (c) Replace this text with your answer. (d) [Variation on 9.2#17]. What do you get when you apply the selection condition Groups-"Ungrouped" and then the projection P1,5 to the database?[5 points]