Q3. Adders

Answer the following questions using only half adders and 2:1 multiplexers. No other logic gates are permitted.

1. (a) Provide the circuit for a 1-bit full adder.

2. (b) Implement a 3-bit adder using half adders and the adder designed in (a). Give the total

   number of half adders used.

3. (c) Implement a circuit which checks if the output of the above 3-bit adder is 12. You

   should not use an adder/comparator to do this.

Hint: 2:1 multiplexers can be used to implement 2-bit logic gates.