A person is walking with constant speed vw, with respect to a moving sidewalk at O'Hare. He is walking in the same direction as the moving sidewalk which has speed vMs with respect to the stationary floor of O'Hare. The time it takes him to walk the length D of the moving sidewalk is tForward. For some unknown reason, once he gets off the moving sidewalk, he turns around and walks in the opposite direction of the moving sidewalk at that same constant speed vw with respect to the moving sidewalk, until he finally exits the moving sidewalk at his original entrance. The time it takes him to walk the length of the moving sidewalk on this return leg is tRack What is tForward in terms of vws ms, and D, as needed?