sql query help please?

Question::List the actorID,firstname,and last name of actors who have ONLY played in drama movies,together with the number of drama movies each actor played. output should be in descending order of number of movies each actor played

the databse is here

MovieInfo(mvid,title,firstname,lastname) where mvid is primary key

Cast(mvID*,actorID*) both of the attribute are primary and forign key

Actor(actorID,firstname,lastname,genre,birthplace) actorID is primary key

Genre(mvID*,genre) mvid and genre both are primary key and mvid is foreign key too

Thanks in advance