1st query will return the following:
Table Name : Total (name, capacity)
$${\begin{array}{|c|c|}\hline
\textbf{name}& \textbf{capacity}\\\hline
\text{Ajmer}& 20 \\ \hline
\text{Bikaner}& 40 \\ \hline
\text{Churu}& 30 \\\hline
\text{Dungargarh}&10 \\\hline
\end{array}}$$
2nd Query will return, Total_avg (capacity) ${\begin{array}{|c|}\hline
25 \\\hline
\end{array}}$
Since sum of capacity $= 100/4=25$
3rd query will be final and it's tuples will be considered as output, where name of district and its total capacity should be more than or equal to $25$
$${\begin{array}{|c|}\hline
\textbf{name}\\\hline
\text{Bikaner} \\ \hline
\text{Churu} \\\hline
\end{array}}$$
Hence, 2 tuples returned.