Driving school abc three cars pass the intersection together

Don't bet1/4 * (1/4) * (1/2) =1/32 on the traffic jam in AB.

BC traffic jam A does not bet1/4 * (1/2) * (3/4) = 3/32.

Don't bet on AC traffic jam B1/4 * (1/2) * (3/4) = 3/32.

All add up to 7/32.