Question 13
If the system of equations
$$
\begin{aligned}
& |x+y|=99 \\
& |x-y|=c
\end{aligned}
$$
has exactly two real solutions $(x, y)$, find the value of $c$.
$$
\begin{aligned}
& |x+y|=99 \\
& |x-y|=c
\end{aligned}
$$
has exactly two real solutions $(x, y)$, find the value of $c$.