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?
Answer Choices
A. 60
B. 75
C. 84
D. 94
E. 109