A problem X is NP-complete if and only if: 1. X is in NP. 2. Any problem in NP is poly-time reducible to X. (I.e., for all YNP,YPX.) (4 points) To prove a problem X is NP-complete, it seems (off-hand, according to part 2 of the definition) that we would have to exhaustively reduce every problem in NP to it. Instead, we typically achieve part 2 of the definition by choosing a single known NP-hard problem and reducing it to X. Explain why this approach suffices