One end of an insulating U-tube is sealed using insulating material. A monoatomic gas at T = 300 K occupies 20 cm length of tube as shown in the figure. The level of mercury on two sides of the tube differs by 5 cm. The other end of the tube is open to atmosphere. Area of cross-section of the tube is uniform and is equal to $0.01m^2.$ The gas in the tube is heated by an electric heater so as to raise its temperature to 562.5 K. Assume no heat is conducted to mercury by gas. The final length of gas column (in cm) is (assume atmospheric pressure is equivalent to 75 cm of Hg column in barometer tube)