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?

The correct option is ₹ 2,600.

Let the number of notebooks purchased by P, Q, X, Y, and Z be represented by the variables p, q, x, y, and z respectively.

From the given information, we can construct the following system of equations:

From statement 2, P and Q together purchased 21 notebooks:
$$p+q=21$$ (Equation 1)

From statement 3, Q purchased 5 notebooks less than P did:
$$q=p-5$$ (Equation 2)

Substituting Equation 2 into Equation 1:
$$p+(p-5)=21$$
$$2p-5=21$$
$$2p=26$$
$$p=13$$

Substituting the value of p into Equation 2:
$$q=13-5=8$$

From statement 5, P purchased 5 notebooks more than X did:
$$p=x+5$$
$$13=x+5$$
$$x=8$$

From statement 1, Z purchased 8 notebooks more than X did:
$$z=x+8$$
$$z=8+8=16$$

From statement 4, X and Y together purchased 28 notebooks:
$$x+y=28$$
$$8+y=28$$
$$y=20$$

Now, let's find the total number of notebooks purchased by all five friends:
$$\mathrm{Total\; Notebooks}=p+q+x+y+z$$
$$\mathrm{Total\; Notebooks}=13+8+8+20+16=65$$

Since each notebook is priced at ₹ 40, the total cost of all the notebooks is:
$$\mathrm{Total\; Cost}=65\times 40=2600$$

Therefore, the total cost of all the notebooks is ₹ 2,600.