A uniform rod is suspended horizontally from its mid-point. A piece of metal whose weight is w is suspended at a distance l from the mid-point. Another weight W 1 ​ is suspended on the other side at a distance l 1 ​ from the mid-point to bring the rod to a horizontal position. When w is completely immersed in water, w 1 ​ needs to be kept at a distance l 2 ​ from the mid-point to get the rod back into horizontal position. The specific gravity of the metal piece is