What additional mass 'm' must be added to regain balance in this scenario when a 100-turn rectangular coil ABCD (in the XY plane) hangs from one arm of a balance, a mass of 500g is added to the other arm to balance the weight of the coil, a current of 4.9 A passes through the coil, and a constant magnetic field of 0.2 T acts inward (in the XZ plane), switching on such that only arm CD of length 1 cm lies in the field?