I need help with problem number 2. I need to reverse this 4 bit adder in order to make it subract.

I apperciate the help.

Logisim: main of Lab3a File Edit Project Simulate Window Help Ful Adder SUM 0 FA Wiring F Splitter SUM 1 FA O Probe Tunnel Pul Resistor SUM 2 Clock FA Constant YD Power + Ground A Transistor SUM 3 Y1 FA Selection: Constant Bits Value 00% 11. You now have a 4-bit adder. (Save this and make a copy, you'll need it in this form for problem 2) 12. From here, extrapolate this to a 32-bit adder Problem 2 [Add/Subtract (11 points) Using the 4-bit adder constructed in the previous problem, modify it so it handles subtracting X bits from Y Bits. Remember, flip the bits and add 1 gives you the negative version of a number Hints You will need a multiplexor for each of the Y bits. The first input to the multiplexor will be the Y bits as they stands... what would the other input be then? 1. 2. Adding 1? Step 10 in problem 1 used a constant pin... does it need* to be constant Logisim: main of Lab3a File Edit Project Simulate Window Help Ful Adder SUM 0 FA Wiring F Splitter SUM 1 FA O Probe Tunnel Pul Resistor SUM 2 Clock FA Constant YD Power + Ground A Transistor SUM 3 Y1 FA Selection: Constant Bits Value 00% 11. You now have a 4-bit adder. (Save this and make a copy, you'll need it in this form for problem 2) 12. From here, extrapolate this to a 32-bit adder Problem 2 [Add/Subtract (11 points) Using the 4-bit adder constructed in the previous problem, modify it so it handles subtracting X bits from Y Bits. Remember, flip the bits and add 1 gives you the negative version of a number Hints You will need a multiplexor for each of the Y bits. The first input to the multiplexor will be the Y bits as they stands... what would the other input be then? 1. 2. Adding 1? Step 10 in problem 1 used a constant pin... does it need* to be constant