A classification problem is considered with observations $x \in \mathbb{R}^2$ and responses $y \in \{0,1\}$. There is a set of axis-aligned rectangle classifiers $F$. Particularly, сlassifier $f_{a,b} \in F$ is defined so: if $a_1 \le x_1 \le b_1 ,\space a_2 \le x_2 \le b_2$ $f(x)=1$ else $f(x)=0$.
The problem is to determine Vapnic-Chervonenkis dimension and growth function for set $F$.
I found here that VC-dimension is 4. But I have no idea how to find growth function.