\[
\begin{gathered}
P\left(\bar{x}-1.96\left(\frac{15000}{\sqrt{300}}\right) \leq \mu \leq \bar{x}+1.96\left(\frac{15000}{\sqrt{300}}\right)\right) \\
=+/-\$ 1697.41
\end{gathered}
\]
So, with \(95 \%\) confidence, the actual average income range for all subscribers would be between \(\$ 81,697\) and \(\$ 78,302\).