What are the values of $a, b$, and $c$ in the matrix addition below?
$\left[\begin{array}{ccc}
4 & 1 & -5 \\
-10 & 2 & 13 \\
3 & 3 & 0 \\
-8 & -9 & 6
\end{array}\right]+\left[\begin{array}{ccc}
-8 & 0 & 6 \\
-4 & 5 & -1 \\
15 & -12 & 3 \\
0 & -3 & 11
\end{array}\right]=\left[\begin{array}{ccc}
-4 & 1 & 1 \\
a & 7 & 12 \\
18 & b & 3 \\
-8 & c & 17
\end{array}\right]$
$\left[\begin{array}{ccc}
4 & 1 & -5 \\
-10 & 2 & 13 \\
3 & 3 & 0 \\
-8 & -9 & 6
\end{array}\right]+\left[\begin{array}{ccc}
-8 & 0 & 6 \\
-4 & 5 & -1 \\
15 & -12 & 3 \\
0 & -3 & 11
\end{array}\right]=\left[\begin{array}{ccc}
-4 & 1 & 1 \\
a & 7 & 12 \\
18 & b & 3 \\
-8 & c & 17
\end{array}\right]$