Answer
$1.2m$
Work Step by Step
We can find the required height difference as follows:
$h=\frac{1}{\rho}(\frac{m_L}{\frac{\pi}{4}D_L^2}-\frac{m_R}{\frac{\pi}{4}D_R^2})$
This simplifies to:
$\implies h=\frac{4}{\pi \rho}(\frac{m_L}{D_L^2}-\frac{m_R}{D_R^2})$
We plug in the known values to obtain:
$h=\frac{4}{\pi(750)}(\frac{1.8}{(0.044)^2}-\frac{3.2}{(0.12)^2})$
$\implies h=1.2m$