4. The 01-swap operation, b, on a binary string S, permutes all occurences of 01 within the original string to 10 (the process is not recursive). For instance: b(0) 0, b(1) 1,b(00) 00, b(01) 10, b(11) 11 b(000) 000, b(001) 010, b(010) 100, b(100) 100 b001 01101 0) 0 10 10 1 10 0 (spacing added for clarity Design a circuit using 2-1 multiplexers that can be used to perform the 01-swap on a k-bit string S-Sk-1 Sk-2 . . . So, where each S, is a bit. (a) First, show the circuit, built using the 2:1 MUX, whose output is the ith bit of b(S) where 0