2.Online video sharing applications become more and more popular. An online video sharing application allows users to record videos, and share with friends. Users need to register in the system by creating an account in the system with a unique username and password. Users are able to add or delete other users into or from their friend lists. The system has three Video Lists for each user. The first Video List contains the videos submitted by the current user. The second Video List contains the videos of friends. The third Video List is composed of recommended public videos from friends or non-friends. Users can write comments for videos of all the three lists. Users can only delete videos of the first list. A rubbish bin is used to contain deleted videos. (4) Write a normal and an exception scenario for the "Video Management" use case. (10') Tip: In this use case, users select a recorded video or record a video directly. After the video is submitted to the system, the format and time duration of the video is checked. If the duration of the video or the format is invalid, a notice is given to the user. Otherwise, the video is converted into a uniform format like MP4. After the format is converted successfully, the video is added to the first list. Finally, the video need to be checked by Administrators of the platform before it can be viewed. At every step of submitting a video, a notice should be sent to the user, e.g., format valid, format converted, checked. (5) Draw a sequence diagram for the normal scenario in question (4). (10 )