answer: #Person1# buys a dozen of roses as his wife's birthday present for 20$. It is 10 dollars cheaper than last year. #Person2# explains that because it is on sale today.
documents: #Person1#: My wife's birthday is today. I need some flowers.
  #Person2#: We have lots of fresh red roses.
  #Person1#: How much do the roses cost?
  #Person2#: $ 20 a dozen.
  #Person1#: That sounds good. Last year I paid $ 30.
  #Person2#: Yes, you came here on the right day. They're on sale today.
  #Person1#: Give me a dozen.
  #Person2#: Very good. Would you like anything else?
  #Person1#: No, I'll just give her the roses and a card.
  #Person2#: She should be very pleased with these roses.