(a) Show that the vectors $\left(\begin{array}{l}1 \\ 0 \\ 2 \\ 1\end{array}\right),\left(\begin{array}{r}-2 \\ 3 \\ -1 \\ 1\end{array}\right),\left(\begin{array}{r}2 \\ -2 \\ 1 \\ -1\end{array}\right)$ are linearly independent. (b) Whi $)$ of the following vectors are in their span? (i) $\left(\begin{array}{l}1 \\ 1 \\ 2 \\ 1\end{array}\right)$, (ii) $\left(\begin{array}{l}1 \\ 0 \\ 0 \\ 0\end{array}\right)$, (iii) $\left(\begin{array}{l}0 \\ 1 \\ 0 \\ 0\end{array}\right)$, (iv) $\left(\begin{array}{l}0 \\ 0 \\ 0 \\ 0\end{array}\right)$.
(c) Suppose $\mathbf{b}=(a, b, c, d)^T$ lies in their span. What conditions must $a, b, c, d$ satisfy?