generate response: That one would be great. Can I get 2 tickets on that train, and the reference number once it's booked?. Intent: book_train. Slots: train-arriveby=21:00, train-bookpeople=2, train-day=sunday, train-departure=cambridge, train-destination=london liverpool street
Response: Certainly. I have now reserved two tickets for you, which you can pay for at the station. Your reference number is 13GQ9S3A .