1. You have been asked to design an Entity-Relationship model for a cinema chain Cinetastic. An informal description has been provided that explains what data they work with We maintain several theatres that are uniquely determined by an identification number. For each theatre we store its name and its address, consisting of postcode, house number, and phone number. A theatre can have several screens but can never have zero screens. We keep the width of the screen in metres and the number of seats available for that screen. Screens are numbered sequentially 1, 2, 3, and so on, in each theatre We need to know, of course, which movie is shown when and on which screen. Thus, each showing of a movie on a screen is documented. It is clear that at any given time only one movie can be shown on a screen. We keep track of the date and time of the show, the number of tickets sold for the show, and the number of unsold tickets for the show. We may have movies and screens in our database that have not (yet) had any showings. A movie may be shown many different times on the same screen, but also at the same time on different screens in the same or different theatres For a movie we maintain a unique identification number (from the IMDB movie database), a title, a release date, a parental guide code in form of a string, and the name or names of the movie's director or directors, respectively. Sometimes our theatres run special promotions for a movie. We need to keep track of which movie is promoted where, when the promotion started, and for how many days it ran. Of course, the same movie can be promoted in various theatres, and not all movies and theatres take part in promotions (a) Give an Enhanced Entity-Relationship model in Chen notation for the above specification. Include cardinality and participation constraints Use the appropriate notation for special attributes including keys. The extent to which your model is correct, minimal, complete and expressive determines the mark you will obtain for this question Entity types and relationships Attributes [14 marks] [14 marks] [13 marks] . Constraints (b) In which situations does one use a Specialisation/Generalisation relationship between several entity types in an Enhanced Entity- [6 marks] Relationship model? (c) Which three levels of database modelling do we distinguish (according [3 marks] to their abstraction level)