1. List all subsets of the set {a, b}.
2. Draw a two-circle Venn diagram, and shade the portion corresponding to the set (S ∪ T')'.
3. There are 16 contestants in a tennis tournament. How many different possibilities are there for the two people who will play in the final round?
4. In how many ways can a coach and five basketball players line up in a row for a picture if the coach insists on standing at one of the ends of the row?