$Q$ is evenly distributed over the volume of a ball of radius $a$ so that the space charge density is proportional to the distance $r$ from the center of the ball. Ie $ρ_v = kr$ where $k$ is a constant. I'm supposed to show that $p_v=kr$

attempt

$$\int E\cdot dA=\int \frac{Q}{4\pi r^2\epsilon_0}\cdot 4\pi r^2=\frac{Q}{\epsilon_0}$$

This is where i'm stuck. Should I use spherical coordinates and just

$$\int \frac{Q}{\epsilon_0}d\tau$$ or $$\iiint \frac{Q}{\epsilon_0}\cdot \rho^2sin\phi d\rho d\theta d\phi$$?

$Q$ is evenly distributed over the volume of a ball of radius $a$ so that the space charge density is proportional to the distance $r$ from the center of the ball. Ie $ρ_v = kr$ where $k$ is a constant. I'm supposed to show that $p_v=kr$

attempt

$$\int E\cdot dA=\int \frac{Q}{4\pi r^2\epsilon_0}\cdot 4\pi r^2=\frac{Q}{\epsilon_0}$$

This is where i'm stuck. Should I use spherical coordinates and just

$$\int \frac{Q}{\epsilon_0}d\tau$$ or $$\iiint \frac{Q}{\epsilon_0}\cdot \rho^2 \sin\phi \, d\rho \, d\theta \, d\phi \, ?$$