A public method named averageRating that takes no parameters and returns a double o This method returns the average of all the Rating of this Song o If the list is empty, the method returns 0.0 o Any invalid rating, ratings of -1, will be ignored during this calculation A public method named removeRatingByReviewer that takes a Reviewer as a parameter and returns void o This method will remove a Rating made for this Song by the given Reviewer o If the reviewer did not rate this song, this method has no effect o If the linked list contains multiple ratings by the reviewer, the method only removes the first instance from the list (ie. the method does not have to handle removing multiple ratings in a sing call)