AB is a uniform rod of length 120 cm , and weight 6kgm.wt its end A is attached to a hinge fixed to a vertical wall. the rod is kept in equilibrium horizontaly by means of a light string , one of it ends is tied to a point c on the rod , where AC=15 cm , and the other end is fixed at a point D on the wall lying above A , and at a distance 20 cm from it. find magnitude of the tension in the string , and the reaction of the hinge.