[add image: logic circuit – two NAND gates (one with A, B and one with $\bar{A}$, B) feeding an AND gate] Outputs of the NAND gates: $\overline{A \cdot B}$ and $\overline{\bar{A} \cdot B}$ $C = \overline{A \cdot B} \cdot \overline{\bar{A} \cdot B} = \overline{A \cdot B + \bar{A} \cdot B}$ (De Morgan's theorem) $C = \overline{B(A + \bar{A})} = \bar{B}$ Truth table: (0,0) → 1, (0,1) → 0, (1,0) → 1, (1,1) → 0