1999 Pascal Problem 23

Al and Bert must arrive at a town 22.5 km away. They have one bicycle between them and must arrive at the same time. Bert sets out riding at 8 km/h, leaves the bicycle and then walks at 5 km/h. Al walks at 4 km/h, reaches the bicycle and rides at 10 km/h. For how many minutes was the bicycle not in motion?

\textbf{(A)}\ 60\quad \textbf{(B)}\ 75\quad \textbf{(C)}\ 84\quad \textbf{(D)}\ 94\quad \textbf{(E)}\ 109

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 Pascal contests here.