$238.$In a vapor$-$liquid contacting equipment, the overall gas phase mass transfer co$-$efficient $($M$.$T$.$C$),$ KG is related to individual co$-$efficients $($KG and KL$)$ as

KG $=1/$KG $+$ m$/$KL

$1/$KG $=1/$KG $+$ m$/$KL

$1/$KG $=1/$KL $+$ m$/$KG

KG $=1/$KL $+$ m$/$KG