3. A college database has the following schema: Class (code, title, number_of_students, department) Lecturer (staff_no, name, supervisor_staff_no) Teaches (code, staff_no) (Total: 12 marks) The table Class records details about classes. The table Lecturer records the staff number of lecturers, their name and the staf number of their supervisor. The table Teaches records who is teaching what class: each row associates a code of a class with a staff code of a lecturer who teaches that class. (a) Identify an attribute in one of the tables that is suitable for manually creating an index. State table & attribute and explain your choice. (2 marks) (b) Write a command to insert a row of data into the class table that only specifies the code to be CS209 and that leaves all other entries unspecified. (1 mark) (c) The Teaches table represents a relationship between Lecturer and Class. What is the degree of the relationship? How can you deduce this from the above provided informa- (2 marks) tion?