A gold ore concentrate consists mostly of silica, along with some arsenopyrite

$($FeAsS$),$ and pyrite $(Fe{S}_2),$ and a very small amount of gold. It analyzes $2\%$ arsenic and

$4\%$ sulphur, which when roasted with air will form $A{s}_2{O}_3$ and $S{O}_2$ vapour and hematite

in the solid residue. If stoichiometric dry air is used, how many kilo$-$mole of oxygen

will have to be blown into the roaster per hundred tonnes of concentrate?