A home owner uses \( 4.00 \times 10^{3} \; \mathrm{m^{3}} \) of methane \( \mathrm{(CH_4}) \) gas, (assume \( \mathrm{CH_4} \) is an ideal gas) in a year to heat his home. Under the pressure of \( 1.0 \; \mathrm{atm} \) and \( 300 \; \mathrm{K} \), mass of gas used is \( x \times 10^{5} \; \mathrm{g} \). The value of \( x \) is __________. (Nearest integer)
(Given \( R = 0.083 \; \mathrm{L\,atm\,K^{-1}\,mol^{-1}} \))
