A home owner uses 4 . 00 × 10 ^ 3 m ^ 3 of methane ( CH _ 4 ) gas,...

A home owner uses $4 . 00 \times {10}^{3}{m}^{3}$ of methane $\left({CH}_{4}\right)$ gas, (assume ${CH}_{4}$ is an ideal gas) in a year to heat his home. Under the pressure of $1 . 0$ atm and $300K$, mass of gas used is $x \times {10}^{5}g$. The value of $x$ is ______. (Nearest integer)

(Given $R = 0 . 083Latm{K}^{- 1}{mol}^{- 1}$)