79By the use of the word ‘determination’, Directive 2001/14 provides, as the Advocate General observed at point 82 of his Opinion, that responsibility for the charging scheme must be reserved to an infrastructure manager which is independent of any railway undertaking. The determination of charges necessarily entails a degree of flexibility on the part of the infrastructure manager, enabling it to adopt, at the very least, decisions involving choices and assessments as to the factors or parameters on which calculations are to be based.