Flat rate is common in broadband access to the Internet in the USA and many other countries. A charge tariff is a class of linear rate, different from the flat rate, where the user is charged by the uploads and downloads (data transfers).
MUI stands for Multilingual User Interface and .dll.mui files are simply libraries(Dlls) that contain resources dedicated to localization : for an application to support multiple languages,dlls containing specific resources must be available eg language resources(arabic,french,english,chinese....
How to Open DLL Files. The Dynamic Link Library, or DLL file, is a mainstay of traditional Windows programming. These files are used by programs to gain additional functionality and libraries without having to have them built-in to the program itself. Oftentimes, DLL files are shared across many different programs.