A Boy has taken a shortcut on which there is a railway track that goes through…

A Boy has taken a shortcut on which there is a railway track that goes through an arrow bridge. When the boy covered 7/16th of the track in the bridge, he heard the whistle of the train. Then he ran out of that bridge, when the train came to that bridge. If he were taken actual root, he would have reached the destination on time, rather taking the shortcut and running out of that bridge. If the boy covers 4km/hr, what was the speed of the train?