4. Recall that integer parity is defined as follows: (8 points) Definition: Every integer is either even or odd. An integer n is even if there exists an integer k such that n= 2k. An integer n is odd if there exists an integer k such that n = 2k +1. Consider the following statement: Let x, y, and z be integers. If x + y + z is odd, then at least one of x, y, or z is odd. (a) Which proof technique should be used to prove the above statement? Briefly explain your answer. (b) Prove the above statement