I need help about my digital logic design laboratory homework.Please the solution be readable and understandable. Thanks.

QUESTION: a. Define and explain 4-bit binary adder-subtractor logic circuit below. Give the detailed theoretical information for the circuit. Draw the logic diagram of the circuit. b. Implement the 4-bit binary adder-subtractor logic circuit on PROTEUS simulation program. By B2 B M 0 CA ; C2 C FA FA FA FA C1 S; $ S 4) (b) 4-bit adder-subtractor FA=4-bit Full-Adder