Where a purchaser decides to conclude a single public contract falling within the scope of Book I intended to meet a need relating to both its activities as a contracting authority and its activities as a contracting entity, the rules of Book I applicable are :
1° The rules applicable to contracting entities, where the need to be met is principally linked to the activity of the contracting entity;
2° The rules applicable to contracting authorities, where the need to be met is principally linked to the activity of the contracting authority or if it is impossible to determine for which activity the public contract is principally intended.