Solution 3.8.7.4 In part (a) the output is D = (A;B)+C = A;B +C In the block diagram of part (b) wehave D = (A+ X);Y: There are lots of answers but the simplest one is to let X = C and Y = B: In other words, wecan rst add C to A and then subtract B and get the same result as rst subtracting B from A and then adding C. 1