Unit 1 - Design a 4-bit adder/subtractor that accepts two 4-bits numbers, A and B, and either add them up (A + B) or subtract them (A - B) depending on a control signal A/S (when the control signal is o perform ADD, otherwise if the signal is 1 then perform SUB). The result will be stored in C. Unit 2 - Design a 4-bit AND/OR unit that accepts two 4-bits numbers, A and B, and either AND them or OR them depending on a control signal A/O (when the control signal is o perform AND, otherwise if the signal is 1 then perform OR bitwise logical operation). The result will be stored in C. Unit 3 - Design a 4-bit ALU using Unit 1 and Unit 2. The control signal A/L will indicate which operation the ALU will perform (when the control signal is o perform Arithmetic, otherwise if the signal is 1 then perform Logic). Unit 4 - Design three 4-bit parallel registers to hold A, B, and C where C keeps the output of the ALU. The registers have a R/W control signal that indicates that they are being written to or read from