What volume of air (in `m^(3)`) is needed for the combustion of `1m^(3)` of a gas having the following composition in percentage volume : `2%` of `C_(2)H_(2), 8%` of `CO, 35%` of `CH_(4), 50%` of `H_(2)` and `5%` of non-combustible gas. The air contains `20.8%` (by volume) of oxygen.