The two parallel circular loops of wire shown in fig each have a radius R = 20 cm and are separated by a distance a = 0.5 cm. The bottom loop is held fixed and the top loop hangs from one end of the arm of an equal arm balance. Since a is much smaller than R, the magnetic field produced by one loop at the other is practically the same as if both were long straight wires. if the current in each loop is 20 A. How much additional mass m must be added to the right-hand pan of the balance to keep the loops separated by 0.5 cm, when the currents are turned on?