mechanics

3 solid hemispheres, each of radius (R) are placed in contact with each other, side by side, such that their flat surfaces rest on the rough horizontal ground . a solid sphere of mass(m) is symmetrically placed on the top of the three hemispheres . find the normal reaction between the solid sphere and any of the three hemispheres, assuming the system to be in stable equilibrium .
.....i am not being able to figure out the exact manner in which the top sphere is placed SYMMETRICALLY