A uniform capillarity tube closed at one end contained dry air trapped by a thread of Mercury 8.5*10-2m long when the tube was held horizontally the length of air column was 5.0*10-2m, when it is held vertically with the closed end downward the length was 4.5*10-2m.

Question

A uniform capillarity tube closed at one end contained dry air trapped by a thread of Mercury 8.5*10-2m long when the tube was held horizontally the length of air column was 5.0*10-2m, when it is held vertically with the closed end downward the length was 4.5*10-2m. 
Determine the volume of the atmospheric pressure.?