A fuel gas consists of $75\%$ butane $($C$4$H$10),10\%$ propane $($C$3$H$8)$ and $15\%$ butene $($C$4$H$8)$ by volume.

It is to be fed to the combustion chamber in $10\%$ excess air at $25$C$,$ where it is completely burnt to carbon dioxide and water. The flue gases produced are to be used to generate $5$ bar steam from water at $90$C$.($c$)$ Determine the actual fuel:air ratio

$($i$)$ by volume $($ii$)$ by mass.