(b) if the predominant activity or each of the predominant activities carried on in such establishment or undertaking or any unit thereof is an industry and the other activity or each of the other activities carried on in such establishment or undertaking or unit thereof is not severable from and is, for the purpose of carrying on, or aiding the carrying on of, such predominant activity or activities, the entire establishment or undertaking or, as the case may be, unit thereof shall be deemed to be an industrial establishment or undertaking;]