Mike has a bookcase with three layers, and the ratio of books placed on the upper, middle and lower layers is $$5:6:4$$. Given that there are $$240$$ books on the middle level,  books should be removed from middle level and added to the lower level so that the number of books on each level can be exactly the same. 
选项为:A:$$48$$  B:$$40$$  C:$$60$$  D:$$80$$  请回答其中一个选项.