A positively charged sphere of radius ${\mathrm{r}}_0$, carries a volume charge density $\mathrm{\delta }$. A spherical cavity of radius $\frac{{\mathrm{r}}_0}{2}$ is then scooped out and left empty. ${\mathrm{C}}_1$ is the centre of the sphere and ${\mathrm{C}}_2$ is that of the cavity. What is the magnitude and direction of electric field at B.