(Solved): A positive point charge (q=+9.51108C) is surrounded by an equipotential surface A, which has a ...

A positive point charge $$\left(q=+9.51\times 10^{?8}\mathrm{C}\right)$$ is surrounded by an equipotential surface $$A$$, which has a radius of $$r_A=1.13\mathrm{m}$$. A positive test charge $$\left(q_0=+4.52\times 10^{?11}\mathrm{C}\right)$$ moves from surface $$A$$ to another equipotential surface $$B$$, which has a radius $$r_B$$. The work done by the electric force as the test charge moves from surface $$A$$ to surface $$B$$ is $$W_{AB}=?8.42\times 10^{?9}$$. Find $$r_B$$. $${\mathrm{r}}_{\mathrm{A}}=$$