The system of linear equations in $x$ and $y$
$$\left( \begin{array} { c c }
5 - \log _ { 2 } a & 2 \\
3 & \log _ { 2 } a
\end{array} \right) \binom { x } { y } = \binom { 0 } { 0 }$$
has a solution other than $x = 0 , y = 0$. What is the sum of all values of $a$? [3 points]\\
(1) 8\\
(2) 10\\
(3) 12\\
(4) 16\\
(5) 20