Apple CEO Tim Cook speaks on Capitol Hill, in Washington, Wednesday, July 29, 2020. Image by GRAEME JENNINGS/POOL/AFP by means of Getty ImagesApple (AAPL) CEO Tim Cook will take the witness stand Friday early morning in the businesss closely watched court fight with “Fortnite” designer Epic. Cooks statement will show to be an essential piece of Apples defense, as it seeks to ward off claims that it operates its App Store as an illegal monopoly.The Associated Press reported that the judge overseeing the case granted Apples demand to enable Cook to be the very first witness to take the stand Friday.Cook, a polished and charming public speaker, will have to reveal that the 30% charge Apple charges larger developers for each sale they make through App Store and the companys control of the market are an important parts of the iOS platform.”What he requires to do is reveal that Apple is not abusing its position with the App Store, which is the only way to get … 3rd party applications onto the iPhone device,” MIT Sloan School of Management teacher Michael Cusumano previously informed Yahoo Finance.Apple gathers its 30% commission from developers for each sale they make through the App Store, though business that earn less than $1 million in earnings only pay 15%. Membership services likewise pay 30% for the very first year of a membership, however that drops to 15% for each subsequent year.Epic says Apples requirement that all app developers utilize its payment system is unreasonable. By allowing designers to provide their own payment choices, the business declares, it can provide products at lower prices. Impressive is also getting in touch with Apple to allow third-party app stores on the iPhone, something Apple states will welcome malware and other destructive apps onto users devices.The conflagration in between the two companies kicked off last August when Epic included its own payment alternative to “Fortnite,” preventing Apples rules. The iPhone maker eliminated the app, and it hasnt been offered on iOS given that. Epic did the same with its Android variation of the app, with Google (GOOG, GOOGL) also taking it down. Google has roughly the exact same rules as Apple for its Play Store.Story continuesApple doesnt break out its quarterly income for the App Store, instead, bundling it with other so-called services like Apple Music, iCloud, Apple TV+, and AppleCare subscriptions. The services segment brought in a massive $53.7 billion in income in 2020 alone. All totaled, Apple saw $274 billion in profits for the year.An expert witness affirmed for Epic that the App Store delights in running margins of 78%, though Apple states just 5% of all apps are paid. Another 9.9% are totally free, but use in-app purchases, like “Fortnite,” while the rest are totally free and supported by ads.Sign up for Yahoo Finance Tech newsletterGot an idea? Email Daniel Howley at email@example.com over via encrypted mail at firstname.lastname@example.org, and follow him on Twitter at @DanielHowley. More from Dan: Follow Yahoo Finance on Twitter, Facebook, Instagram, Flipboard, SmartNews, LinkedIn, YouTube, and reddit.