KEAM 2017 Physics and Chemistry Paper

A train of length L move with a constant speed Vt. A person at the back of the train fires a bullet at time t = 0 towards a target which is at a distance of D (at time t =0) from the front of the train (on the same direction of motion). Another person at the front of the train fires another bullet at time t = T towards the same target. Both bullets reach the target at the same time. Assuming the speed of the bullets, Vb, are same, the length of the train is