An open glass tube is immersed

An open glass tube is immersed in mercury in such a way that a length of $8 \mathrm{~cm}$ extends above the mercury level. The open of the tube is then closed and sealed and the tube is raised vertically up by addition $46 \mathrm{~cm}$. What will be length of the air column above mercury in the tube now ?

(Atmospheric pressure $=76 \mathrm{~cm}$ of $\mathrm{Hg}$ )