Is interest on borrowed capital which, according to Article 35(4) of the Fourth Council Directive 78/660/EEC of 25 July 1978, may be included in the production costs to the extent that it relates to the period of production, part of the taxable amount of an application within the meaning of Article 5(6) of Sixth Council Directive, that is to say, part of the ‘cost price' within the meaning of Article 11A(1) of the Sixth Directive and/or the incidental expenses within the meaning of Article 11A(2) of the Sixth Directive?