Section 48(1)(b) in The West Bengal Industrial Infra-Structure Development Corporation Act, 1974
(b)where the person to be served is a firm, if the document is addressed to the firm at its principal place of business, indentifying it by the name or style under which its business is carried on, and is either-(i)sent under a certificate of posting or by registered post, or(ii)left at the said place of business;