Shentong paid your basic postage, so you should attach 5 yuan to the courier who sent the courier to the school, because Ren 'ai is not within the delivery scope. You can also reach Tong Yuan, which is also the money of 5 yuan, for the same reason as Shentong.

SF Express and Renai are within the scope of delivery. If you send something from Beijing to Tianjin, I suggest you choose to collect it, because it is 15 yuan. If you buy something from Taobao, the shopkeeper will charge you 20 yuan. In fact, the postage is 15, which can save 5 yuan. Only Beijing to Renai is 15. Mail from other places 20+

And e-mail EMS.