Please help me on this problems...

1) Let P be the set of all U.S. presidents, and let G be the set of all ordered pairs (a,b) in P X P such that b succeeded a in office. Is G the graph of a function? Explain.

2) Prove that for each set X there is a unique function from the empty set to X, regardless of whether or not X is nonempty. Also prove that there are no functions from X to the empty set if X is nonempty.