1998 Gauss 8 Problem 14

Stephen had a 10:00 a.m. appointment 60 km from his home. He averaged 80 km/h for the trip and arrived 20 minutes late for the appointment. At what time did he leave his home?

\textbf{(A)}\ 9:35 \text{ a.m.}\quad \textbf{(B)}\ 9:15 \text{ a.m.}\quad \textbf{(C)}\ 8:40 \text{ a.m.}\quad \textbf{(D)}\ 9:00 \text{ a.m.}\quad \textbf{(E)}\ 9:20 \text{ a.m.}

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Gauss contests here.