Q6. A satellite revolving around a planet in stationary orbit has time period 6 hours. The mass of planet is one-fourth the mass of earth. The radius orbit of planet is : ( Given $=$ Radius of geo-stationary orbit for earth is $4.2 \times 10 ^ { 4 } \mathrm {~km}$ )\\
(1) $1.4 \times 10 ^ { 4 } \mathrm {~km}$\\
(2) $1.05 \times 10 ^ { 4 } \mathrm {~km}$\\
(3) $8.4 \times 10 ^ { 4 } \mathrm {~km}$\\
(4) $1.68 \times 10 ^ { 5 } \mathrm {~km}$