Consider the below schematic of a 4-bit binary adder-subtractor. Consider two 4- bit sequences A (A3 A2 A1 A0) = 1001 and B (B3 B2 B1 BO) = 0010. Study the schematic and explain in detail how the subtraction process (A-B) happens. Proof the result and comment on it. (15 points) Cout B3 A3 Full Adder $3 C2 B2 A2 Full Adder S2 C1 B1 A1 Full Adder $1 8 CO Figure 1. 4-bit binary adder-subtractor AO Full Adder SO Cin -K