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- Apple's stock fell Monday morning after EU regulators slapped the company with a $2 billion fine.
- The fine is part of the EU's push to get Apple to open up its App Store.
- Investors are trying to figure out how much opening the App Store may hurt the company long term.
European regulators have fined Apple $2 billion for violating antitrust rules.
But that's not the worst news Apple is dealing with Monday.