A static system consisting of air, water, oil and mercury is shown in the figure. If Q is open to the atmosphere, the gauge pressure at P is ______ kPa (rounded off to one decimal place).
Consider \(g = 10 \text{ m/s}^2\), \(h_1 = 0.5\) m, \(h_2 = 0.7\) m, \(h_3 = 0.8\) m, density of water \(= 1000 \text{ kg/m}^3\), \(SG_{oil} = 0.9\) and \(SG_{mercury} = 13.6\) (where SG is specific gravity).
