4.1. Sales revenues

The Group has concluded long-term master agreements containing basic quantitative arrangements per annum and options. Each time before the year begins they are made specific and divided into quarters and the terms for exercising the options are defined. Operationally, the arrangements for specific quarters are made through quarterly negotiations. Therefore, the Group benefits from the exclusion prescribed by IFRS 15 and does not disclose the transaction price attached to the obligations to make performances not fulfilled under these agreements.