SQL language

For a Movies database with a Person entity and a Movie entity which have a relationship Acts_In, suppose we wanted to add a count of the number of movies for each person -that is, how many movies has an actor played a role in. How should we model this? Add the count as a regular attribute of the Person entity Add the count as a regular attribute of the Acts_In relationship Add the count as a derived attribute of the Acts_In relationship Add the count as a derived attribute of the Person entity