The figure shows a homogeneous rock layer of thickness \(100\ \text{m}\). A vertical borehole is drilled through the layer and gravity is measured at the top point \(A\) and at the base point \(B\). If the difference in measurements between \(A\) and \(B\) is \(5\ \text{mGal}\), find the density \(\rho\) of the rock layer in g/cc (ignore terrain corrections).
