Answer
$1.42 \times10^3 \ km$
Work Step by Step
The first rocket must go 10.5 orbits in the time that it takes the other rocket to go 10. Since radius is directly related to the period raised to the 2/3 power, we find:
$(\frac{10}{10.5})^{2/3}=\frac{r}{45,800}$
$ r = 44,334\ km$
Thus, we find the difference is:
$h = 45,800\ km - 44,334 \ km =1,465 \ km$