A tank contains water with air above it; a gauge on the tank reads 80 kPa (gauge pressure of the air). From the water space a tube runs out and down so that the water column falls 30 cm to the water–mercury interface in the left arm of a U-tube. In the right arm the mercury (SG 13.6) stands h higher than that interface, and above the mercury there is a 75 cm column of oil (SG 0.72) open to the atmosphere at its top. Determine the differential height h of the mercury column (answer in m).