You are in a subway station in New York City. Describe the activities involved in purchasing a subway ticket from a ticket vending machine, using the UML Activity Diagrams. Once you open up a buying session, the machine will ask you what you want to do: purchase a new ticket, or replenish the money available on an existing ticket. 
When purchasing a new ticket, the machine will ask you how many trips you want to purchase. After the passenger specifies the number of trips, the machine will display the price per trip, and ask for the payment. The passenger can pay either with a card or with cash. When using a credit card, the machine will need to contact the Credit Card Company to validate the card and authorize the payment. When paying with cash, the machine will need to be able to dispense the change (if needed). After the payment is processed, the machine will dispense the ticket and complete the buying session.
If the passenger wants to replenish the money available on an existing ticket, the machine will ask to introduce the existing ticket in the slot. The machine will display the existing amount of money that is still available on the ticket. Then, it will ask the passenger how much money he/she would want to add to the ticket. The passenger will be able to pay by credit card or cash. From this point on, the same steps as above will be repeated in terms of authorizing the payment on the credit card, or dispensing the change if paid with cash. After the payment is processed, the machine will dispense the ticket and complete the buying session.

Required minimum 3-4 page