Consider the following solution that proves that for any int…

Consider the following solution that proves that for any integers a and b, the difference a−b is even or odd.Case 1: a and b have the same parity (both even or both odd). Then a−b is even.Case 2: a and b have different parity (one even, one odd). Then a−b is odd.All possibilities are covered, so the statement holds.Which of the following proof strategies was followed above?