Solution 8.7.3.1.
Using the given information, apply the exponential distribution. Since 10 arrive on average in one hour then you would expect 1 to arrive in 6 minutes.
With \(\mu = 6\) minutes,
\begin{equation*}
P(X \gt 9) = 1 - F(9) = e^{-9/6}.
\end{equation*}