Create verilog code for this 4bit adder/subtracter. It must be implimented exactly as is, do NOT simplify or use XOR. Please give detailed comments of what each part of the code does. This is meant to be compatable with Quartus Prime software. I will be very grateful for your help.

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