An inverted U-tube manometer is connected to two horizontal pipes A and B through which water is flowing. The vertical distance between the axes of these pipes is 27 cm. When oil of specific gravity 0.85 is used as a gauge fluid, the vertical heights of water columns in the two limbs of the inverted manometer (when measured from the respective center lines of the pipes) are found to be the same and equal to 35 cm. Determine the difference in pressure between the pipes.