I got it :) sorry for all the confusion guys..and thanks a ton !! :):)
Sry.I mistakenly wrote M=N-nY instead of M=N+ny
When u use this the identity will look like: Y= Ā+cY-nY-bi. (U can also consider tax also)
Y=1/(1-c+n)*Ā-bi/(1-c+n)
→i= Ā/b-Y(1-c+n)/b
In closed economy n=0
i=Ā/b-Y(1-c)/b
Now, compare!