Two satellites `S_1` and `S_2` are revolving round a planet in coplanar and concentric circular orbits of radii `R_1` and `R_2` in the same direction respectively. Their respective periods of revolution are 1 hr and 8 hr. The radius of the orbit of satellite `S_1` is equal to `10^4` km. Their relative speed when they are closest , in kmph is :

Options

A. `pi/2xx10^4`
B. `pixx10^4`
C. `2pixx10^4`
D. `4pixx10^4`

Answer

B