[Yhippa]

One of the things I learned was from the Singapore test question (about Cheryl's birthday) which was to parse the question for any clues. What tipped me off was the requirement that either or both of them could get the correct answer to satisfy the problem statement. Once I figured that out I came to the conclusion to try out the truth table where one participant holds their answer constant and the other does a negation of their answer. The truth table worked out.

I have to say I feel somewhat inadequate coming to the answer experimentally as opposed to what others did here.