At present the elementary liquid$-$phase reaction A$+$B$->$R$+$S takes place in a plug flow reactor using equimolar quantities of A and B$.$ Conversion is $96\%,$ CA$0=$ CB$0=1$ mol$/$liter$.$ If a mixed flow reactor ten times as large as the plug flow reactor were hooked up in series with the existing unit, which unit should come first and by what fraction could production be increased for that setup?