Solve for the unknowns in the vector equation below.

$6 \left[\begin{matrix} 2 \cr a \cr -6 \cr \end{matrix}\right] +4 \left[\begin{matrix} 5 \cr 9 \cr b \cr \end{matrix}\right] = \left[\begin{matrix} c \cr 4 \cr 4 \cr \end{matrix}\right]$

$a=$

$b=$

$c=$