Consider a database to store information for a social network website. The features and constrains of database are described below:

• Every user has a unique user ID, full name, age, and phone number.

• Every group has a unique group ID and a name.

• Every group has only one user that moderates the group.

• A user must be a member of at least one group, and groups may contain zero or

  more members.

• Users can create zero or more albums.

• An album has a unique album ID, a creation date, and a name.

• An album is owned by exactly one user.

• An album can contain zero or more media files.

• Every media file, has a unique URL, a date, and a caption.

• Photos are a type of media file, but also have the encoding (e.g., JPEG) and the

  size of the photo.

• Videos are a type of media file, but also have the codec (e.g., MPEG), the length,

  and the bitrate of the video.

• A media file may belong to at most one album.

  The Entity-Relationship Diagram of the database is shown in Figure 1. This diagram is not complete and has some mistakes. You need to find and correct any mistakes (i.e., missing key for an entity, wrong line type, missing an attribute, missing a relationship) in the given ER diagram. Draw a complete and correct diagram.

group id name Group moderates member of > User user id age phone # owns Album date crea name album id contains URL Media date added Photo Video bitrate encoding size codec ength