Suppose you have a friend at a different university who is taking a similar math course to one you are taking. He is having problems understanding the subtle differences between permutations and combinations, as well as the accompanying formulas nCr and nPr. Also, he does not understand the Fundamental Counting Principle. In order to help, you pick three questions from your book that deal with these concepts and write him an email.
The three questions you must solve for your friend are: