There was an airplane crash, every single person on board died, but yet two people survived. how is this possible?

7. design a circuit with three inputs (x, y, and z) representing the bits in a binary number, and three outputs (a, b, and c) also representing bits in a binary number. when the input is 1, 2, or 3, the binary output should be one lesser than the input. when the input is 4, 5, or 6, the binary output should be one greater than the input. when the input is 0, the output is 0, and when the input is 7, the output is 7. show your truth table, all computations for simplification, and the final circuit.