Three balls have masses and positions as follows:

• Ball 1: m₁ = 1.2 kg, x₁ = 0.4 m, y₁ = 0.7 m.
• Ball 2: m₂ = 2.1 kg, x₂ = -0.4 m, y₂ = 0.7 m.
• Ball 3: m₃ = 1.7 kg, x₃ = 0.1 m, y₃ = 0.2 m.

Where is the center-of-mass of the system? How does it move if you change the mass of any of the balls?