A spring scale hangs from a cord that is attached to a hook in the ceiling. A 10 kg object hangs from a second cord connected to the bottom of the scale. The weights of the cords and the scale are negligible. 

(a) What is the reading of the scale? 

(b) The 10 kg object is removed and the upper cord detached from the hook. Two people grasp the free ends of the cords and pull until the scale reading is the same as in (a). With what force is each person pulling?