Consider the function f which has four inputs a,b,c,d and one output such that the output is a 1 if and only if the number of 1s in the inputs is even. (a) Write the canonical product-of-sums expression for f. Do not use the shorthand notation. (b) Write the canonical product-of-sums expression for f in shorthand notation. (c) Write the canonical product-of-sums expression for f' in shorthand notation