answer: #Person2# helps #Person1# buy a two liters bottle of Coke.
documents: #Person1#: Excuse me. How much for a two liter bottle of Coke?
  #Person2#: 87 cents.
  #Person1#: How come so cheap?
  #Person2#: It's on sale this week.
  #Person1#: I'll take one. And here is a dollar.
  #Person2#: Here's your change.
  #Person1#: Thank you very much.