Due date is 3/10. If you don't have the textbook, you may make an appointment with me to borrow my textbook. 

(1)	Modify the Verilog code shown on Page 162 so that the circuit on Figure 4.13 (Four-bit adder-subtractor) on page 138  is implemented. Basically you need to replace existing module ripple_carry_4_bit_adder() with your adder_subtractor module. In your implementation, please eliminate output V in the adder_subtractor circuit. Note that C0 is same as M, and NOT an independent input. In your test bench, include the following test cases: inputs A(1001) +/- B(0011) and inputs A(0011) +/- B(1001). Please use your pen to mark each of the cases in your waveforms.

(2)	Problem 4.52 on Page 180. Note that you need to first describe the design steps (showing how you obtain the Boolean functions that are to be used in your continuous assignment code. In your test bench, include the following test cases: inputs A(1000) +/- 1 and inputs A(01111) +/- 1. Please use your pen to mark each of the case in your waveforms.