Four students asked their teacher, Mr. Carter, to line up with them to take a picture.  ①If Mr. Carter does not want to stand on either end, how many different ways can they line up for the picture?  ②If Mr. Carter insists on standing on one of the $2$ ends, how many different ways can they line up for the picture? 
Overseas Competition->Knowledge Point->Counting Modules->Law of Addition and Multiplication->Queuing Problems
①$$3\times 4\times 3\times 2\times 1=72$$ ,  ②$$2\times 4\times 3\times 2\times 1=48$$ . 