A printer charges a set-up fee of 2000 rupees plus 4 rupees for each book…

Step 1. For 100 books. $A(100) = \dfrac{400 + 2000}{100} = 24$ rupees per book.

Step 2. For 1000 books. $A(1000) = \dfrac{4000 + 2000}{1000} = 6$ rupees per book.

Step 3. The limit. Divide the top and the bottom by $n$: $A(n) = 4 + \dfrac{2000}{n}$. As $n \to \infty$, $\dfrac{2000}{n} \to 0$, so $A(n) \to 4$ rupees per book.