solve part C

Two spherical shells have a common center. The inner shell has radius R1=5.00cm and charge q1=+5.00106C; the outer shell has radius R2=15.0cm and charge q2=7.00106C. Both charges are spread uniformly over the shell surface. Take V=0 at a large distance from the shells. What is the electric potential due to the two shells at the distance r=2.50cm from their common center. Express your answer with the appropriate units. Part B What is the electric potential due to the two shells at the distance r=10.0cm from their common center. Express your answer with the appropriate units. What is the electric potential due to the two shells at the distance r=20.0cm from their common center. Express your answer with the appropriate units