Emily sees a ship traveling at a constant speed along a straight section of a river. She walks parallel to the riverbank at a uniform rate faster tha the ship. She counts 210 equal steps walking from the back of the ship to the front. Walking in the opposite direction, she counts 42 steps of the same size from the front of the ship to the back. In terms of Emily's equal steps, what is the length of the ship?
<spanclass=′latex−bold′>(A)</span>70<spanclass=′latex−bold′>(B)</span>84<spanclass=′latex−bold′>(C)</span>98<spanclass=′latex−bold′>(D)</span>105<spanclass=′latex−bold′>(E)</span>126