A flat circular rotor (disc) has two holes. The first has a diameter of 15 mm, made to a radius of 78 mm, and placed at 0° with respect to a horizontal radial reference marked on the disc. The second hole has a diameter of 9 mm, made at a radius of 79 mm, and placed at 90° (counterclockwise) with respect to the same reference. The disc is going to balance by making a third hole. With respect to the same horizontal radial reference marked on the disc, determine the angle (counterclockwise) where the third hole must be made. Give your answer in degrees (°).