3. (30 pts) Create an ER diagram for the following situation (Hint: At least one weak entity type is involved) For this exercise we'll model a blog system (like blogger.com), where there are many users which can have different blogs.

We want to model Users, their Blogs, the Postings on each blog, and the Comments for each posting.

For each user, we keep its username (identifier), password and Name, divided into first, middle, last.

For each blog, we keep its id (identifier), title, the date it was created, and the number of posts (which can be calculated); we also keep track of which user created which blog; a blog is created by exactly one user, and a user can create one or more blogs.

For each Posting, we keep its id (identifier), the blog it belongs to (postings belong to exactly one blog, and blogs may have zero or more postings), its time stamp and its contents.

For each Comment, we keep its number (which uniquely identifies comments for the same posting, but not all comments in general), time stamp and contents. We also keep track the user who made the comment (comments are made by exactly one user, and a user can make

zero or more comments), and the posting the comment refers to (comments refer to exactly one posting, and postings can have zero or more comments).