A fluid of unknown density is used in two manometers-one sealed-end, the other across an orifice in a water pipeline. The readings shown here are obtained on a day when barometric pressure is 756mm...

A fluid of unknown density is used in two manometers-one sealed-end, the other across an orifice in a water pipeline. The readings shown here are obtained on a day when barometric pressure is 756mm Hg. What is the pressure drop (mm Hg) from point (a) to point(b)?