Why does the meem sakinah had specific chapter in tajweed?

Question
Why does the meem sakinah had specific chapter in tajweed?
Answer
The meem sakinah has a specific chapter just like the noon sakinaah. This is like for example in the chapter of noon Sakinah the rules are related specifically to the noon saakinah followed by the different arabic letters from which we can know the rules of the noon saakinah.  Similarly there is a different chapter for the meem sakinah in which the meem is followed by the different Arabic letters from which we can get to know the meem sakinah rules. It is put in different chapters in order not to confuse the different rules concerning the noon and meem.  The letters that affect the meem saakinah rules are different than the letters that affect the noon saakinah rules. 

Wassalam Alaikum Wa Rahamtullah