A combinational circuit is divided into two subcircuits

N$1$

and

N$2$

as shown.

A combinational circuit is divided into two subcircuits N$1$ and N$2.$ The contents of subcircuit N$1$ are unknown and subcircuit N$2$ contains one exclusive$-$OR gate and one OR gate.

A$,$ B$,$ and C enter subcircuit N$1,$ which outputs D$,$ E$,$ and F$.$

D$,$ E$,$ and F enter subcircuit N$2,$ which outputs Z$.$

Within subcircuit N$2,$ E and F enter the OR gate.

Within subcircuit N$2,$ D and the output of the OR gate enter the exclulsive$-$OR gate.

The exclusive$-$OR gate outputs Z$.$