A student is standing in the school's court yard and estimates that a rock at a point 3.20 m west and 7.45 m north of the southeast corner has a mass of 100 kg. The student finds another rock of estimated mass 75.0 kg at 9.00 m west and 2.30 m north of the same point, and a last rock of estimated mass 45.0 kg at 5.00 m west and 3.00 m north. Find the coordinates of the center of mass and apply you know about finding center of mass to each rock independently.