Consider only transitions involving the $n=1$ through $n=5$ energy levels for the H atom (where the energy level spacings below are not to scale).
$$\begin{aligned}
&\begin{aligned}
& n=5 \\
& n=4 \\
& n=3 \\
& n=2
\end{aligned}\\
&7\\
&n=1
\end{aligned}$$
(a) How many emission lines are possible, considering only the five quantum levels?
(b) Photons of the highest frequency are emitted in a transition from the level with $n=\quad$ to a level with $n=$
(c) The emission line having the longest wavelength corresponds to a transition from the level with $n=\ldots$ to the level with $n=$