Furthermore, given is the family of lines $h _ { a } : \vec { X } = \left( \begin{array} { l } 0 \\ 0 \\ 1 \end{array} \right) + \mu \cdot \left( \begin{array} { l } 1 \\ a \\ 0 \end{array} \right)$ with $\mu \in \mathbb { R }$ and $a \in \mathbb { R }$. Prove that $g$ and $h _ { a }$ are skew lines for every value of $a$.