1) it is not possible to carry out an audit referred to in Article 53 (5) for the reasons on the part of an operator, 2) the entity entitled to carry out an audit referred to in Article 53 (5) refuses to express its opinion due to circumstances preventing the formulation of an opinion for the reasons on the part of an operator, 3) the entity entitled to carry out an audit referred to in Article 53 (5) expresses a negative opinion or an opinion with reservations, 4) there are significant differences between the amount of fees established by an operator and the amount of fees verified under paragraph 3 – the President of UKE shall establish the amount of fees for telecommunications access or their maximum or minimum level applying the methods referred to in paragraph 1a. The above fees shall be established in a separate decision. 5. The President of UKE while establishing fees for telecommunications access shall take into account the promotion of efficiency, sustainable competition and the assurance of maximum benefits for end users as well as the recovery of justified costs. 6. If an operator has incurred expenses on a new investment project, including on nextgeneration network roll-out, the President of UKE while determining fees for telecommunications access, shall take into account the investment made by that operator and shall allow a reasonable rate of return on capital employed in a new investment project, taking into account any risks specific to a particular new investment project. Article 40. 1. The President of UKE may, in line with the objectives referred to in Article 24 point (2a) and by means of a decision, impose on an operator with significant market power the obligation to set cost-based fees for telecommunications access. 1a. The President of UKE shall indicate in the decision referred to in paragraph 1 the methods for verification and establishing charges referred to in paragraph 3 and 4. 2. An operator on whom the obligation referred to in paragraph 1 was imposed shall submit to the President of UKE its justification of the amount of cost-based fees. 3. In order to verify whether the amount of fees applied by an operator referred to in paragraph 1 is correct, the President of UKE may apply verification methods indicated under paragraph 1a. 4. Where the verification referred to in paragraph 3 reveals that the amount of fees established by an operator is not correct, the President of UKE shall establish the amount of fees or their maximum or minimum level applying the methods for establishing fees referred to in paragraph 1a, taking account of the promotion of efficiency, sustainable competition and the assurance of maximum benefits for end users. The fees shall be established in a separate decision. 5. If an operator has incurred expenses on a new investment project, including on nextgeneration network roll-out, the President of UKE while determining the level of fees or their maximum or minimum amount in a decision referred to in paragraph 4, shall take into account the investment made by that operator and shall allow a reasonable rate of return on capital employed in a new investment project, taking into account any risks specific to a particular new investment project. Article 41. 1. The fees for mutual use of interconnected networks related to the implementation of number portability between the networks should take account of the costs incurred. 2. The fees for mutual use of interconnected networks and for telecommunications access related to carrier selection should take account of the costs incurred.