A man standing on a platform finds that a train takes 3 seconds to pass him and another train of the same length moving in the opposite direction takes 4 seconds. The time taken by the trains to pass each other will be `2 3/7s e con d s` b. `3 3/7s e con d s` c. `4 3/7s e con d s` d. `5 3/7s e con d s`