Answer the question number 3
3. The volume charge density within a volume V is $\mathrm{\rho }\left(\mathrm{r}\right)$. What is the force on a small test charge ${\mathrm{q}}_0$ placed outside the volume  having position vector $\overrightarrow{{\mathrm{r}}_0}$ with respect to the same origin considered to specify the position vector of the charge distribution within the volume.