Two thin conducting concentric shells of radii \( R_1 \) and \( R_2 \) are shown in the figure. The inner shell carries a charge \( +Q \) and the outer shell is neutral. Then the correct statement is: 
Two condensers \( C_1 \) & \( C_2 \) in a circuit are joined as shown in the figure. The potential of point A is \( V_1 \) and that of point B is \( V_2 \). The potential at point D will be:
