a) Find all solutions of the system of equations (1)-(3). - Furthermore, provide a system of equations that differs from the given one by exactly one coefficient and

b) has infinitely many solutions,

c) which is not satisfied by any triple of real numbers $x, y, z$.

$$
\begin{gathered}
2 x+3 y+z=1 \\
4 x-y+2 z=2 \\
8 x+5 y+3 z=4
\end{gathered}
$$