Mass density of a solid sphere is $\rho$. Radius of sphere is R. The gravitational field at a distance $r$ from the center of the sphere inside it is

Question

$$(a)\;\frac{4 \rho G \pi r}{3} \quad (b)\;\frac{4 \rho G \pi r^2}{3} \quad (c)\;\frac{4 \rho G \pi R^3}{3r^2} \quad (d)\;\frac{ \rho G R^3}{\pi r}$$