Four cars travel at constant speed along a road. Three of them (A, B and C) travel in one direction, and the fourth, D, in the opposite direction.
Car A passes B and C at 9:00h and 10:00h, respectively, and crosses car D at 11:00h.
Car D crosses car B and car C at 13:00h and 15:00h, respectively.
At what time did car B pass car C?
Bonus point: can you solve this geometrically?