d
$\beta=\frac{-\Delta \mathrm{P}}{\frac{\Delta \mathrm{V}}{\mathrm{V}}}$
$\Delta \mathrm{P}=-\beta \frac{\Delta \mathrm{V}}{\mathrm{V}}$
$\rho \mathrm{gh}=-\beta \frac{\Delta \mathrm{V}}{\mathrm{V}}$
$10^3 \times 10 \times \mathrm{h}=-9 \times 10^8 \times\left(-\frac{0.02}{100}\right)$
$\Rightarrow \mathrm{h}=18 \mathrm{~m}$