Identify the primary key and foreign keys in the following relational schema. (24) (a) Twitter User (User ID. fname. Iname, join date) Tag (Tag ID, Tag name, creationDate) User Tag Relationships (User ID. Tag ID associationDate numberOfAssociations) Write your answer below. Select the PK from existing attributes. If there is no FK in a table, state "None"): Twitter User: PK: Tag: PK: User Tag Relationships PK: FK: FK: FK