to service operators; (b) lease out part of a local loop and equipment facilities; (c) rent a leased line; (d) lease out an antenna site and part of a cable duct; (e) publish delivery terms and tariff information; (f) lease out part of a terrestrial mass communications or broadcasting network; (g) organize national and international roaming; (h) use cost-oriented pricing based on cost calculations; (i) provide pre-selection for international calls in a mobile network; (j) use appropriate methodology of costaccounting; (k) keep separate accounts on its activities; (l) interconnect an information and communications network to another information and communications network; and (m) provide universal service. (3) Specific conditions relating to the allocation of numbers that may be attached to licences where justified and with due respect for the principle of proportionality include(a) designation of the service for which the number is used, including any requirements in regard to the provision of that service; (b) effective and efficient use of numbers; (c) requirements in regard to number 55