answer: #Person2# helps #Person1# change 4000 yuan to US dollars.
documents: #Person1#: Is this the foreign exchange department?
  #Person2#: Yes, can I help you?
  #Person1#: I need some US Dollars.
  #Person2#: What kind of currency have you got?
  #Person1#: RIB. By the way, what is the exchange rate today?
  #Person2#: One US Dollars in cash is equivalent t0 7. 9 Yuan.
  #Person1#: And I want to change 4000 Yuan.
  #Person2#: Minus the fee. Here are your dollars. Please sign here.
  #Person1#: OK, thank you.