Methane is oxidized with air to produce formaldehyde in a continuous reactor. A competing reaction is the combustion of methane to form $C{O}_2.$

$C{H}_4(g)+O_2$HCHO$(g)+H_{2}O(v)$

$C{H}_4(g)+2O_{2}C{O}_2+2H_{2}O(v)$

A flowchart of the process for an assumed basis of $100$mol of methane fed to the reactor is shown here.How the outlet number of mole is determined?