Four Particles Are Located at Each Corner of a Square

Multiple Choice

Four particles are located at each corner of a square of length 2 cm.If a mass M is located at (x₁,y₁) = (-1 cm,1 cm) ,a mass 2M is located at (x₂,y₂) = (1 cm,1 cm) ,a mass 2 M is located at (x₃,y₃) = (1 cm,-1 cm) ,and a mass M is located at (x₄,y₄) = (-1 cm,-1 cm) ,where is the center of mass located?

A) (0 cm,0 cm)
B) (1/3 cm,0 cm)
C) (0 cm,1/3 cm)
D) (2 cm,0 cm)
E) (0 cm,2 cm)