A home owner uses $4.00 \times 10^3 \mathrm{~m}^3$ of methane $\left(\mathrm{CH}_4\right)$ gas, (assume $\mathrm{CH}_4$ is an ideal gas) in a year to heat his home. Under the pressure of 1.0 atm and 300 K , mass of gas used is $x \times 10^5 \mathrm{~g}$. The value of $x$ is $\_\_\_\_$
(Nearest integer) (Given $\mathrm{R}=0.083 \mathrm{~L} \mathrm{~atm} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ )