A particle carrying charge \(+q\) is placed at the center of a thick-walled conducting shell that has inner radius \(R\) and outer radius \(2 R\) and carries charge \(-4 q\). A thinwalled conducting shell of radius \(3 R\) carries charge \(+4 q\) and is concentric with the thick-walled shell. Defining \(V=0\) at infinity, calculate all distances from the particle at which the electrostatic potential is zero.