3. What are the possibilities for the number of incongruent solutions of the system of linear congruences
$$\begin{array}{l}
a x+b y \equiv c(\bmod p) \\
d x+e y \equiv f(\bmod p)
\end{array}$$
where $p$ is a prime and $a, b, c, d, e$, and $f$ are positive integers?
3. $0,1, p$, or $p^{2}$