In matrix equation $[A] \{X\}=\{R\}$,

$[A] = \begin{bmatrix} 4 & 8 & 4 \\ 8 & 16 & -4 \\ 4 & -4 & 15 \end{bmatrix} \{X\} = \begin{Bmatrix} 2 \\ 1 \\ 4 \end{Bmatrix} \text{ and} \{ R \} = \begin{Bmatrix} 32 \\ 16 \\ 64 \end{Bmatrix}$

One of the eigen values of matrix $[A]$ is

1. $4$
2. $8$
3. $15$
4. $16$