In circumstances where expenditure of a branch established in one Member State is exclusively used for the transactions of its principal establishment established in another Member State, must the provisions of Article 17(2), (3) and (5) and Article 19(1) of the Sixth Directive 77/388/EEC, incorporated in Articles 168, 169 and 173 to 175 of Directive 2006/112/EC, be interpreted to the effect that the Member State in which the branch is registered is to apply to that expenditure the branch's deductible proportion, determined according to the transactions carried out in the Member State in which it is registered and according to the rules applicable in that State, or to apply the proportion applicable to the principal establishment, or to deduct a specific proportion combining the rules applicable in the Member States in which the branch and the principal establishment are registered, with regard in particular to a possible option mechanism for imposing value added tax on transactions?