Case T-168/05: Judgment of the Court of First Instance of 30 September 2009 — Arkema v Commission (Competition — Agreements, decisions and concerted practices — Market for Monochloroacetic acid — Decision finding an infringement of Article 81 EC — Market sharing and price fixing — Imputability of the unlawful conduct — Principle that penalties must fit the offence — Obligation to state the reasons on which the decision is based — Fines — Proportionality — Gravity and duration of the infringement — Deterrent effect — Actual impact on the market — Attenuating circumstances — Role of follower — Aggravating circumstances — Repeated infringement)