Design a 4-bit adder/subtractor that accepts two 4-bits numbers, A and B, and either add them up (A + B) or subtract them (A B) depending on a control signal A/S (when the control signal is 0 perform ADD, otherwise if the signal is 1 then perform SUB). The result will be stored in C.

Please do so using only and, or, nand, nor, xor, and xnor gates