Four masses A, B, C, and D are attached to a shaft and revolve in the same plane. The masses are 12 kg, 10 kg, 18 kg, and 15 kg respectively, and their radii of rotation are 40 mm, 50 mm, 60 mm, and 30 mm. The angular positions of masses B, C, and D are 60°, 135°, and 270° from mass A. Find the magnitude and position of the balancing mass at a radius of 100 mm.