Given that $f(x) = x^2 - 13$ and $g(x) = 6 - x$, find $(f - g)(3)$, if it exists.
Select the correct choice below and, if necessary, fill in the answer box to complete your choice.
A. $(f - g)(3) = \Box$ (Simplify your answer.)
B. The value for $(f - g)(3)$ does not exist.