explain the details to solve this problem please

Pure chlorobenzene is contained in a flask attached to an open-end mercury manometer. When the flask contents are at 58.3C, the height of the mercury in the arm of the manometer connected to the flask is 771mm and that in the arm open to the atmosphere is 78 mm. At 103C. the mercury level is 639mm in the arm connected to the flask and 210mm in the other arm. Atmospheric pressure is 755mmHg