One mole of methane undergoes complete combustion in a stoichiometric amount of air. The reaction proceeds as CH$4+2$O$2$ CO$2+2$H$2$O$.$ Both the reactants and products are in gas phase. H$298=-730$ kJ$/$mole of methane. Mole fraction of water vapour in the product gases is about

$0\mathrm{.}19$

$0\mathrm{.}33$

$0\mathrm{.}4$

$0\mathrm{.}67$