\textbf{137.} Matrix $A = \begin{bmatrix} 5 & 2 & -1 \\ 4 & 3 & -2 \\ 1 & 6 & 7 \end{bmatrix}$ is written as the sum of a symmetric matrix and a skew-symmetric matrix. The determinant of the symmetric matrix is:
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\hfill (1) $16$ \hfill (2) $18$ \hfill (3) $22$ \hfill (4) $24$ \hfill
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