The approximate height from the surface of earth at which the weight of the body becomes $\frac { 1 } { 3 }$ of its weight on the surface of earth is :\\
[Radius of earth $\mathrm { R } = 6400 \mathrm {~km}$ and $\sqrt { 3 } = 1.732$ ]\\
(1) 3840 km\\
(2) 4685 km\\
(3) 2133 km\\
(4) 4267 km