answer: #Person1# buys carnations and roses because it's Mother's Day and also #Person1#'s Mom's birthday. #Person2# suggests putting sugar and vitamin C in the water to make flowers stay fresh.
documents: #Person1#: How much are the carnations and the roses?
  #Person2#: One dollar for each carnation and one and a half for each red rose.
  #Person1#: Then I'd like a dozen red carnations and half a dozen red roses.
  #Person2#: I bet it's for your mother, as it's Mother's Day today.
  #Person1#: Well, not completely true. It happens to he her birthday.
  #Person2#: Oh, really? I guess she must be very happy to receive these beautiful carnations from you.
  #Person1#: Yeah, she will. She really likes flowers. So I buy her some every year. I'd just wish they would stay fresh longer than they do.
  #Person2#: Put a little sugar and vitamin C in the water. They'll stay fresh for days.
  #Person1#: Really? I'll tell my mother. And thanks for your suggestion.
  #Person2#: That's all right. Happy birthday to your mother!