Problem: A 3.00 kg mass is located at x = 2.0 cm and y = -4.0 cm. A 3.00 kg mass is located at x = -5.0 cm and y = 2.0 cm. A 4.00 kg mass is located at x = -3.0 cm and y = -3.0 cm. Where is the center of mass (x, y)?
A: (-0.10 cm, -0.50 cm)
B: (-2.1 cm, -1.8 cm)
C: (+2.1 cm, -1.8 cm)
D: (-2.1 cm, +1.8 cm)
E: (+1.1 cm, -2.0 cm)