Physics center of mass

All three disks are made of sheet metal of the same material, and the diameters are 1.4m , 2.8m , and 4.2m . Assume that the x-axis has its origin at the left-most point of the left-most object and it points to the right.

Determine the location of the center of mass of the system shown in figure one. (figure one depicts three spheres, increasing from size from left to right.)

Repeat the calculation for three solid spheres all made of the same metal and having the same diameters as in part A..