This is an NP-complete problem
Only true if the OP was looking for an optimum solution. He isn't:
Subset size is not matter,
Behooves you to read the actual question.
With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.