There are $15$ apples on each of $6$ trees. Five children want to pick some apples. Two of them each picks $13$ apples, and the others each picks $20$ apples. How many apples are left on the trees? 
选项为:A:$$4$$  B:$$6$$  C:$$8$$  D:$$12$$  E:$$15$$  请回答其中一个选项.