If the matrix
\[
\begin{bmatrix}
1 & 3 & 1 \\
2 & 1 & \alpha \\
0 & 1 & -1
\end{bmatrix}
\]
is singular.
Given a function
\( f(x) = \int_{0}^{x} (t^2 + 2t + 3)\, dt \),
\( \forall x \in [1, \alpha] \).
If \( m \) and \( n \) are the maximum and minimum values of the function \( f(x) \),
then the value of \( 3(m - n) \) is: