No problem it is not uncommon to see questions like this. There may be some clues in the other lecture notes and text on the sections you are in that might infer more detail then the question as posted. Is your class being taught by the professor or a teaching assistant?
I hope you see my point regarding saying "any four subsets of the universal set" possibly containing the the null set and also there is nothing to specify whether the subsets intersect which would change the number of regions. So I am pretty sure I could prove any number of regions from 4 to 14 just depending on if I include the null set and how I chose to intersect the subsets.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675
Last edited by ctbram : 11-02-2011 at 08:49 PM.