Five friends $P$ , $Q$ , $X$ , $Y$ and $Z$ purchased some notebooks. The relevant information is given below :

1. $Z$ purchased 8 notebooks more than $X$ did.
2. $P$ and $Q$ together purchased 21 notebooks.
3. $Q$ purchased 5 notebooks less than $P$ did.
4. $X$ and $Y$ together purchased 28 notebooks.
5. $P$ purchased 5 notebooks more than $X$ did.

If each notebook is priced ₹ 40, then what is the total cost of all the notebooks?