Helium is stored in cylinders, each cylinder having a volume $1.5{\mathrm{m}}^3$ at a gauge pressure of $1.5\times {10}^6{\mathrm{Nm}}^{-2}$. A ballon is filled with helium at atmospheric pressure to a volume $600m^3$ , using gas stored in the cylinders. Temperature of helium inside the balloon and that of the surrounding are both ${27}^{0}c$ . Given that
 Density of air at  ${27}^{0}c$= $\text{ 1. }2{\mathrm{Kgm}}^{-3}$
 Atmospheric pressure = ${10}^5{\mathrm{Nm}}^{-2}$
 Mass of helium = $4\mathrm{g}/\mathrm{mol}$

Universal gas Constant $\left(\mathrm{R}\right)=8.3\mathrm{J}{\mathrm{mol}}^{-1}{\mathrm{K}}^{-1}$
$g=10{\mathrm{ms}}^{-2}$