14) 
    a)  \begin{align*}
        y &= ( \bot \cdot \bar d + \top \cdot d) \cdot \bar c + (\bar a \cdot \bar d + (a \cdot b) \cdot d) \cdot c \\
          &= d \cdot \bar c + (\bar a \cdot \bar d + (a \cdot b) \cdot d) \cdot c
        \end{align*}
    b)  Abbildung \ref{fig:netz}
        \begin{figure}[h]
        \centering
        \begin{circuitikz} \draw
        (0,3) node (a) {$a$}
        (0,2) node (b) {$b$}
        (0,1) node (c) {$c$}
        (0,0) node (d) {$d$}
        (2,2.5) node [or port] (or1) {}
        (a) -- (or1.in 1)
        (b) -- (or1.in 2)
        (4,2.5) node [not port] (not1) {}
        (or1.out) -- (not1.in)
        (6,1.75) node [and port] (and1) {}
        (not1.out) -- (and1.in 1)
        (c) -- (and1.in 2)
        (2,0) node [not port] (not2) {}
        (d) -- (not2.in)
        (8,0.875) node [or port] (or2) {}
        (and1.out) -- (or2.in 1)
        (not2.out) -- (or2.in 2)
        (10,0.875) node (y) {$y$}
        (or2.out) -- (y);
        \end{circuitikz}
        \caption{Schaltnetz}
        \label{fig:netz}
        \end{figure}

15)
    a)  $0 + 0 = 0$
    b)  $1 \cdot 1 = 1$
    c)  $| B^n | \cdot 2 = 2 \cdot 2^n = 2^{n+1}$
    d)  $(x_1 \cdot x_2 \cdot \bar x_3) + (x_3 \cdot x_4) + \bar x_2$ ist wahr für $(0, 0, 0, 0)$
    e)  $\lceil \log_2(n) \rceil$