A nonconducting sphere of radius `R = 5 cm` has its center at the origin O of the coordinate system as shown in (Fig. 3.112). It has two spherical cavities of radius `r = 1 cm`, whose centers are at `0,3 cm` and `0,-3 cm`, respectively, and solid material of the sphere has uniform positive charge density `rho = 1 // pi mu Cm^-3`. Calculate the electric potential at point `P (4 cm, 0)`.
.