Hello there!

Greetings!

Centre of mass is given by = (m1x1+m2x2+m3x3+m4x4)/(m1+m2+m3+m4)

where m is the respective mass and x is the respective distance with respect to A ( in metres)

the diagonal of a square is 0.8 metres therefore using pythogoras law each side is of a distance 0.56 metres.

therefore centre of mass is = (8*0+2*0.56+4*0.8+2*0.56)/(8+2+4+2)=0.34 metres from A.

thankyou