Two Cambridge graduates, Peter and Paul, meet for the first time in 20 years.
Peter asks, "How've you been?"
Paul says, "Great! I'm married now and have three daughters."
Peter asks, "How old are they?"
Paul answers, ""The product of their ages is 72, and the sum of their ages is the same as the number on that building over there."
Peter says "Uh... I still don't know."
Paul says, "My oldest just started to play the piano."
Then Peter says, "Really? My oldest is the same age!"
How old are the daughters?