Exhibit 99(e)(5)(vix) IRREVOCABLE UNDERTAKING To: RWE AG, Opernplatz 1, D-45128 Essen, Germany ("RWE") and GBV Funfte Gesellschaft fur Beteiligungsverwaltung mbH, Opernplatz 1, D-45128 Essen, Germany (the "Offeror"), (a wholly owned subsidiary of RWE)...