Please create a verilog code for the 4 bit adder /subtracter in the picture. The code needs to be exactly as the circuit in the picture is. DO NOT USE XOR GATES OR SIMPLIFY THE CIRCUIT IN THE CODE. please also give detailed comments. This is suppose to be compatable with quartus prime. This is very much appreciated, thank you.

4 bit adder and Subtracter K to Bo So Si Az B2 -S2 A3 B3 S3 Cout