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, UpdateTariff. 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.