19. (12 points) The one-way driving time T between a school's new and old campuses depends only on road conditions. A sample of 100 observations was collected with the following results:

\begin{center}
\begin{tabular}{ | l | l | l | l | l | }
\hline
T (minutes) & 25 & 30 & 35 & 40 \\
\hline
\end{tabular}
\end{center}

\begin{center}
\begin{tabular}{ | l | l | l | l | l | }
\hline
Frequency & 20 & 30 & 40 & 10 \\
\hline
\end{tabular}
\end{center}

(I) Find the probability distribution of T and the mathematical expectation ET;\\
(II) Professor Liu drives from the old campus to the new campus for a 50-minute lecture, then immediately returns to the old campus. Find the probability that the total time from leaving the old campus to returning is no more than 120 minutes.