Answer
$T = 2.15\times 10^4~s$
Work Step by Step
We can find the period:
$T^2 = \frac{4\pi^2~r^3}{GM}$
$T = \sqrt{\frac{4\pi^2~r^3}{GM}}$
$T = \sqrt{\frac{(4\pi^2)(4.20\times 10^7~m)^3}{(6.67\times 10^{-11}~N~m^2/kg^2)(9.50\times 10^{25}~kg)}}$
$T = 2.15\times 10^4~s$
