A half adder is implemented with XOR and AND gates. A full adder is implemented with two half adders and one OR gate. The propagation delay of an XOR gate is twice that of an AND$/$OR gate. The propagation delay of an AND$/$OR gate is $1\mathrm{.}2$ microseconds.

A $4-$bi pple$-$carry binary adder is implemented by$,$ four full adders. The total propagation tim his $4-$bit binary adder in microsecondsx