Find energy and momentum coefficient($alpha$ and $beta$) for laminar flow

We have laminar flow and the equation of velocity is:

$$U_r=K(R^2-r^2)$$

Where $U_r$ is velocity at radius $r$ and $R$ is radius of the pipe and $K$ is constant.

I tried to draw the figure:

In this figure $(R^2-r^2)$ lies on the shaded area.

$$alpha=frac{int v^3 . dA}{V^3.A} quad beta=frac{int v^2. dA}{V^2.A}$$

So $A=pi(R^2-r^2)$. But I don’t know how to calculate these integrals to find $alpha$ and $beta$

Edit: I guess I should use polar system to calculate integral but I don’t have the value of $V$ (Which is average velocity)