A U-tube mercury manometer is connected to a venturimeter to measure the pressure drop of water flowing through a pipeline. If the difference in the mercury levels in the tube is \(20 \mathrm{~cm}\), then determine the pressure drop, given that the density of mercury \(=1.4 \times 10^{4} \mathrm{~kg} / \mathrm{m}^{3}\) and that of water \(=1 \times 10^{3} \mathrm{~kg} / \mathrm{m}^{3}\).