1.
If B=(52a1021a3k)B = \begin{pmatrix} 5 & 2a & 1 \\ 0 & 2 & 1 \\ a & 3 & k \end{pmatrix} is the inverse of a 3×33 \times 3 matrix AA, then the sum of all values of aa for which A=10|A| = 10 is: