Design three versions of the combinational circuit whose input is a4-bit number whose output is the 2's complement of the inputnumber, for each of the following cases:
a) The circuit is a simplified two-level circuit, plus inverters asneeded for the input variables.
b) The circuit is made up of four identical two-input, two outputcells, one for each bit. The cells are connected in cascade, withlines similar to a carry between them. The value applied to therightmost carry bit is 0.
c) The circuit is redesigned with carry lookahead-like logic inorder to speed up the circuit in part (b) for use in largercircuits with 4n input bits.