52Furthermore, it is also necessary to reject the plea of inadmissibility concerning the Commission’s argument in the defence that the overall percentage of sales to unrelated domestic customers for all products should be taken into account in order to determine whether the prices were comparable. That argument amounts only to a background matter put forward by the Commission in its defence in the light of which the complaint of the applicants as to the sales volumes must be read. It should be borne in mind that the defence serves, in particular, to inform the Court of the factual and legal context of the case before it, which forms the backcloth to the contested decision and with which the Court, unlike the parties, is not familiar. Furthermore, the fact that a decision against which an action for annulment is brought omits to mention background matters which would subsequently be brought before the Court in the course of the presentation, by a party, of the circumstances in which the dispute before it has evolved does not, as such, attest a failure to observe the duty to state the reasons for the contested decision (see, to that effect, judgment of 8 March 2007, France Télécom v Commission (T‑340/04, EU:T:2007:81, paragraph 79). It follows that the fact that that argument was not raised at the administrative stage has no effect on the present case.