An air bubble is at the bottom of the lake at $40\;m$ deep where the temperature is $0^{\circ}C$. The bubble rises to the surface where the temperature is $20^{\circ}C$ If it's volume at the bottom is $50\;cm^3$, what is its volume at the surface?
Note:
Specific gravity of mercury is $13.6$
1 Atmospheric pressure = $76\;cm$ of Mercury