List out all the possible ways in order.  $C A E$  $C E A$  $A C E$  $A E C$  $E C A$  $E A C $ 
There are three books, Chinese, Math, and English. Sissy wants to put them in bookcase. How many ways are there for three books to put? 
Options:
(1) $$6$$ 
(2) $$5$$ 
(3) $$4$$ 
(4) $$3$$ 