Exercise 2: In the previous use case diagram you created for the Library Administration System, what type of relationship can you use to show that the librarian can do whatever a library patron can (with some extra additions)? Show that relationship and refine the diagram accordingly. Exercise 3: Draw a use case diagram for a ticket distributor for a train system. The system includes two actors: a traveler, who purchases different types of tickets, and a central computer system, which maintains a reference database for the tariff. Use cases should include: BuyOneWayTicket, BuyWeeklyCard, BuyMonthlyCard, Update Tariff. Also include the following exceptional cases: Time-Out (i.e., traveler took too long to insert the right amount), TransactionAborted (i.e.,traveler selected the cancel button without completing the transaction), DistributorOutOfChange, and DistributorOutOfPaper