okay. So, we are talking about 89¢ per container as singles. There is a case of 12 for $8.64. To find the unit price per container for that, we can divide the price by the number of containers. 8.64/12 is 0.72. That's 72¢ per container by the case. That's cheaper than buying it by a single. Let's subtract. 89 - 72 is 17. There. 17¢ per container is saved by buying the oil case.