The atmospheric pressure \(P\) in pounds per square inch (psi) is given by

\[P=14.7 e^{-0.21 a}\]

where \(a\) is the altitude above sea level (in miles). If a city has an atmospheric pressure of \(13.23 \mathrm{psi}\), what is its altitude?

(Recall that \(1 \mathrm{mi}=5,280 \mathrm{ft}\).)