The planet Mars has two moons, if one of them has a period 7 hours, 30 minutes and an orbital radius of $9.0 \times 10^3 \mathrm{~km}$. Find the mass of Mars.
$\left\{\right.$ Given $\left.\frac{4 \pi^2}{G}=6 \times 10^{11} N^{-1} m^{-2} k g^2\right\}$