Can you please help with the following database question

Q.2 Consider the following relational schema corresponding to a movie database. Artist(aid, name) Movie(mid, title, director) Role(aid, character name, mid) a) Write an SQL statement which would return the number of artists who have performed in 3 or more movies directed by the director "John Smith" b) Write an SQL statement which would return the distinct names of all artists who have acted in some movie directed by "John Smith" but have never performed in any movie directed by directed "Bob Green