RMS velocity of one mole of an ideal gas was measen at different temperatures. A graph of $\left(\mu_{\mathrm{ma}}\right)^{-2}$ (on $Y$-sdi) and $T(\mathrm{~K})$ ( on $X$-axis) gave straight line passing through the origin and its slope is $249 \mathrm{~m}^2 \mathrm{~s}^{-2} \mathrm{~K}^{-1}$. What is the molar mass ( in kg mol${ }^{-1}$ ) of ideal gas? $ \left(R=83 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}\right) $