a) Forward-looking costs shall refer to the costs an efficient operator would incur to provide a given service. b) The cost basis shall be established by using any of the following cost modelling methods: i) Long-run incremental cost (LRIC); ii) Long-run incremental cost plus (LRIC+), which allows for joint and common costs; or, iii) Retail minus. 4) Tariffs for Wholesale Roaming shall not be unduly discriminatory in accordance with Article 6(1). In practice, this requires that the difference between the retail tariff for Mobile Communications Services of the provider of Wholesale Roaming, and the provider’s tariffs for Wholesale Roaming services to the New Licensee, would allow an efficient New Licensee to sustain a competing Mobile Communications Service. 5) Tariffs for Wholesale Roaming shall be deemed anti-competitive if it is likely to create, or has the likely effect of creating, a Margin Squeeze, in accordance with the Telecommunications Competition Directive No. 9/2021 adopted by the Authority. 6) Tariffs for Wholesale Roaming shall distinguish and separately account for: a) Fixed, one-off charges for the establishment and implementation of a Wholesale Roaming service; b) Periodic rental charges for usage; and, c) Variable charges for supplementary services. 7) Tariffs for Wholesale Roaming shall be charged according to the kind of service delivered: a) Voice service shall be charged by the minute; b) Mobile messaging service (SMS and MMS) shall be charged per capacity or per text message; and, c) Data service shall be charged according to usage or capacity; unless otherwise agreed by the parties. 8) The provider of Wholesale Roaming shall file Wholesale Roaming tariffs with the Authority for approval. 9) Pursuant to Article 45 (4) of the Proclamation, the Authority may direct a Wholesale Roaming provider to delay the effectiveness of any tariff filed pursuant to Sub-Article 8 of this Article, until the Authority has approved said tariff. 10) Within thirty (30) working days from the receipt of a request for approval of Wholesale Roaming tariffs pursuant to Sub-Article 8 of this Article, the Authority shall respond in writing, and either: d) Approve the filed tariffs; e) Not approve the filed tariffs; or, f) Announce its intention to initiate a regulatory proceeding to review and ensure that those tariffs are lawful in accordance with Article 45 of the Proclamation, this Directive, and any other applicable Directive adopted by the Authority, following 11