1. In a standard set of double-six dominoes, there is exactly one domino for every possible (unordered) pair of numbers from 0 to 6 (including doubles, i.e. a domino with two fives.) A "hand" of dominoes is another word for a set of dominoes. (a) How many dominoes are there (show your work)? (b) How many five-domino hands are there? (c) How many five-domino hands contain no domino with a 0? (d) How many five-domino hands contain at least one double? (e) How many five-domino hands contain no domino with a value greater than 3? (f) How many dominoes are in a standard set of double-n dominoes (where there is exactly one domino for every possible unordered pair of numbers from 0 to n including doubles.)