A water filled manometer is attached to the inlet and the test section of a low speed wind tunnel which has the contraction ratio of 3. what would be the pressure difference between the inlet and the test section in terms of inches of water in order to maintain the dynamic pressure of 20lb/ft^2 at the test section? Density of air = 0.00237slug/ft^3 and density of water = 1.94 slug/ft^3, g=32.2ft/sec^2