(r) Revenue recognition The Group recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred and/or service has been performed, the price is fixed or determinable and collection is reasonably assured. In accordance with ASC 605-45, the Company adopts net presentation method for its revenue, under which revenues are net of business tax, related surcharges and value added tax. Revenues presented in the consolidated statements of comprehensive income include revenues from mobile value added services that are comprised of consumer mobile security, mobile games and live mobile social video platform, advertising services, enterprise mobility and other services. Mobile Value Added Services Revenues Consumer mobile security revenues Consumer mobile security revenues are derived principally from providing premium mobile security and productivity services to end users. The basic functions of security and productivity services, including anti-virus, anti-malware, anti-spam, privacy protection, data backup and recovery are free of charge. The customers are charged for updating the anti-virus database on a pay-per-use basis or paying a fee to subscribe to the premium security and productivity services including continuous update of anti-virus database, continuous update of the semantics of anti-spam, and advanced privacy protection on a monthly, quarterly, semi-annually or annually basis. The Group recognizes revenue for premium services considered to be software-related (e.g., mobile security services) in accordance with industry specific accounting guidance for software and software-related transactions. For premium services where the customer does not take possession of fully-functioning software (e.g., mobile productivity services), the Group recognizes revenue pursuant to ASC 605, Revenue Recognition. Provided collectability is probable, revenue is recognized over the usage period which is the same for software-related services and services where software is incidental to the provision of