Design a combinational circuit with inputs a, b, c, d and outputs w, x, y, z. Assume that the inputs a, b, c, d represent a 4-bit signed number (2s

complement). The output is also a signed number in which is the 2s complement of the input. (Here design means to determine Boolean expressions for each of the output bits w, x, y, z. No need to draw out a circuit diagram)