5) To calculate the cost of providing a Retail Service, the Authority may use the Downstream Retail Cost of the vertically integrated Telecommunications Operator as a proxy for the Downstream Retail Cost of an efficient retail competitor. 6) The Authority shall use the Telecommunications Operator’s current year costs, or where available, regulatory accounting costs, subject to reasonable adjustments if these are from a prior year, as the source of information to calculate the Downstream Retail Cost of the vertically integrated Telecommunications Operator. 7) The Authority shall use any of the following cost modelling methods to establish the cost basis of a Retail Service: a) Long‐run incremental cost (LRIC); or b) Long‐run incremental cost plus (LRIC+), which allows for joint and common costs. 20. Investigation of Anti‐Competitive Practices and Adjudication 1) For the Authority to identify allegations that raise substantive and well‐grounded concerns, and therefore to direct its resources appropriately, a complaint shall be specific and cite the specific articles of the Proclamation, this Directive, or competition laws, that form the basis for the complaint. 2) Complaints shall include specific information about services, prices, costs, terms and conditions of service, copies of contracts or invoices, and any other information that may support the allegation of anti‐competitive practices. 3) Within twenty (20) working days of receiving a written complaint, the Authority shall respond to all parties to the complaint, indicating whether: a) It considers that there is not enough evidence to initiate and investigation; or b) Is providing ten (10) working days to the party accused of wrongdoing, to respond to such allegations; or c) Is initiating a proceeding to investigate the allegations in accordance to the procedure established in Articles 34 and 36 through 38 of the Proclamation and this Directive. 4) Pursuant to Article 52 (3) of the Proclamation, the Authority shall have the power to adjudicate all complaints against any Telecommunications Operator, and the power to assess appropriate remedies for any violation of the terms of the Proclamation, this Directive, or any applicable Directive adopted by the Authority. 5) Where the Authority decides to impose remedies or sanctions, these shall be proportionate, non-discriminatory, and transparent. PART SEVEN MERGERS AND ACQUISITIONS 21. Control of Mergers and Acquisitions 1) No agreement or arrangement of an acquisition or merger, involving directly or indirectly, an authorized provider of Telecommunications Services, may come into effect prior to the approval of the Authority. 11