So when a question ask "What is |ABC|" it is not really asking that? Why would the question not ask what is the maximum that |ABC| could be?
So when you say 11 you are saying "there is at most 11 elements in ABC"?
Oh btw I just realized that I missed out one key premise.... AuBuC=109 I think I can solve it now. I keep getting psyched out by these problems and choking really.
EDIT: nope still can't solve it. LOL