A column of Hg of 100 mm in length is contained in the middle of a narrow tube 1 m long which is closed at both ends. Both the halves of the tube contained air at a pressure of760 mm of Hg. By what distance (in mm) will the column of Hg lie displaced if the tube is held vertical? Assume decrease in length of mercury column to be negligible, also take the process at constant temperature (isothermal process).