Answer
$v = 1.23\times 10^4~m/s$
Work Step by Step
We can find the speed:
$K = \frac{1}{2}mv^2 = \frac{GMm}{2r}$
$v^2 = \frac{GM}{r}$
$v = \sqrt{\frac{GM}{r}}$
$v = \sqrt{\frac{(6.67\times 10^{-11}~N~m^2/kg^2)(9.50\times 10^{25}~kg)}{4.20\times 10^7~m}}$
$v = 1.23\times 10^4~m/s$
