Let $a_1=\left[\begin{array}{c}1\\ 4\\ -1\end{array}\right],a_2=\left[\begin{array}{c}-6\\ -20\\ 2\end{array}\right],$ and $b=\left[\begin{array}{c}5\\ 4\\ h\end{array}\right].$ For what value$($s$)$ of $h$ is $b$ in the plane spanned by $a_1$ and $a_2$

The value$($s$)$ of $h$ is$($are$).($Use a comma to separate answers as needed.$)$