So if I am making n decisions, and exactly five of them are a specific
   decision, how many different total decision combinations result in
   that?
   I think that the answer is combinations, nCr, but I'm really confused
   around that.
   Combinations says, if I put n things in a bag, and try out all the ways
   of taking r of them out, and consider the same items in a different
   order to be the same ....
   Anyway I think it is permutations, not combinations ...