A body of mass m is placed at distance 'x' from the centre of Earth such that x < R. If R is the radius of the Earth, the gravitational force F acting on the body is related to the mean density of Earth 'd' as
1
\(\frac{2}{7} \pi G (dm)\)
2
\(\frac{2}{5} \pi G (dm x^2)\)
3
\(\frac{4}{3} \pi G (dm x)\)
4
\(\frac{4}{3} \pi^2 G (dm x^3)\)