For Q1, can we simply assume the points are in order of ABC? I chose D since the order could be BAC, although nevertheless Alex’s speed will be 30 and therefore A will still be the answer. But I’m just curious if the order BAC can also be considered.

Just to be clear, AC would be 300 (AC = BC - BA = 500 - 200)

The question has been adjusted to eliminate this ambiguity.