If $A = \begin{bmatrix} 10 & 2k +5 \\ 3k - 3 & k +5 \end{bmatrix}$ is a  symmetric matrix, the value of $k$ is __________________.

1. $8$
2. $5$
3. $-0.4$
4. $\frac{1 + \sqrt{1561}}{12}$