Ruby method using class and instances

I'm just starting out with Ruby and trying to write a method that returns "Title was written by author", where title and author are variables. I think I'm close, but I'm not sure what to add at this point.

class Book
  def set_title_and_author=(title, author)
    @title = title
    @author = author
  end
  def set_title_and_author
  "#{@title} was written by #{@author}"
  end
end