Let $f, g : \{ 0, 1 \} \to \{ 0, 1 \}$ each be a D18: Map such that
| (i) | \begin{equation} f(0) = f(1) = 0 \end{equation} |
| (ii) | \begin{equation} g(0) = g(1) = 1 \end{equation} |
Then
| (1) | \begin{equation} g(f(0)) = g(f(1)) = g(0) = 1 \end{equation} |
| (2) | \begin{equation} f(g(0)) = f(g(1)) = f(1) = 0 \end{equation} |