A narrow tube of uniform base, closed at one end has some air entrapped by a small quantity of water. If the pressure of the atmosphere is 760 mm of Hg and vapour pressure of H2O at 12∘C and 35∘C are 10.5 mm Hg and 42 mm Hg respectively and the length of the air column is 10 cm at 12∘C, what will be its length at 35∘C?