Answer
$41Km$
Work Step by Step
We know that
$P_{max}=P_{at}+\rho_{earth}gh_{max}$
This can be rearranged as:
$h_{max}=\frac{P_{max}-P_{at}}{\rho_{earth}g}$
We plug in the known values to obtain:
$h_{max}=\frac{1.2\times 10^9-1.01\times 10^5}{(3.0\times 10^3)(9.81)}=41Km$
