In the old west, a marshal riding on a train traveling 35.0 m//s observes a duel between two men standing on the Earth 55.0 m apart parallel to the train. The marshal’s instruments indicate that in his reference frame the two men fired concurrently.
a) Which of the two men, the first one the train passes (A) or the second one (B) must be arrested for firing first? That is, in the gunfighter's frame of reference, who fired first?
b) How much earlier did he fire?
c) Who was struck first?