generate response: I need to leave after 21:15. Can you book this for four people? I need a reference number.. Intent: book_train. Slots: train-bookpeople=4, train-day=monday, train-departure=broxbourne, train-destination=cambridge, train-leaveat=21:15
Response: Booking was successful, the total fee is 71.59 GBP payable at the station. Reference number is : UPJBMQ32 .