$4$: $1\mathrm{.}3$#$11$ Determine if $b$ is a linear combination of $a_1,a_2,$ and $a_3$

$a_1=\left[\begin{array}{c}1\\ -2\\ 0\end{array}\right],a_2=\left[\begin{array}{c}0\\ 1\\ 2\end{array}\right],a_3=\left[\begin{array}{c}5\\ -6\\ 8\end{array}\right],b=\left[\begin{array}{c}2\\ -1\\ 6\end{array}\right]$