answer: #Person2# helps #Person1# to buy a berth ticket to Shanghai leaving at 20:05.
documents: #Person1#: I'd like to have a berth ticket to Shanghai.
  #Person2#: Which train do you want?
  #Person1#: The 19:00 train.
  #Person2#: Sorry. There aren't any tickets available for the 19:00 train.
  #Person1#: When is the next train to Shanghai?
  #Person2#: The next train will leave at 20 : O5.
  #Person1#: How much is the ticket?
  #Person2#: 180 yuan.
  #Person1#: Here is 200 yuan.
  #Person2#: Here are your ticket and change.