发现Amazon更新了条例，以前大部分都是5%，diaper & wipes是20% for Amazon mom。
现在，那个5%有希望变成15%，if you subscribe more than 5
subscriptions arriving in a month. 当然，尿布什么的20%了，不会更打折，但是可
以算作5个subscription之一从而帮助其它的4个打折。 https://www.amazon.com/gp/subscribe-and-save/dp/info.html
The more you subscribe, the more you save.
1 - 4 subscriptions arriving in a month Save 5%
5 or more subscriptions arriving in a month Save 15%
Diapers & wipes count toward your 5 items, but aren’t eligible for more
than 5% savings except for Amazon Mom members.
