First, take a look at this link to understand the Principle of
Inclusion and Exclusion: http://en.wikipedia.org/wiki/Inclusion%E2%80%93exclusion_principle
Next, make a list of all the subsets:
First, take a look at this link to understand the Principle of
Inclusion and Exclusion: http://en.wikipedia.org/wiki/Inclusion%E2%80%93exclusion_principle
Next, make a list of all the subsets: