There are $18$ bottles of water in each of $10$ boxes. Six customers want to buy some botlles of water. Four of them buy $30$ bottles of water, and two of them buy $20$ bottles of water. How many bottles of water are left in the boxes 
选项为:A:$$10$$  B:$$20$$  C:$$30$$  D:$$35$$  E:$$40$$  请回答其中一个选项.