The following relational database schema contains information about actors, plays and roles performed: Actor (actor_id, name, year_born) Play (play_id, title, author, year_written) Role (actor_id, character name, play_id) Where: Actor is a table of actors, their names and the year they were born. Play is a table of plays, giving the title, author and year written for each play. Role records which actors have performed which roles (characters) in which plays. Attributes actor_id and play_id are foreign keys to Actor and Play respectively. All three attributes make up the primary key since it is possible for a single actor to play more than one character in the same play. (a) [5 marks] Write a SQL query that returns the number of actors who have performed in three or more different plays written by the author August Wilson". (b) [5 marks] Write a SQL query that returns the names of all the actors who have performed some play by the author Chekhov" and have never performed in any play written by author "Shakespeare". The list should not contain duplicates but need to be ordered in alphabetical manner