In the problem discussed in the text, find `E - r` expressions for inside and outside points.

Explanation

To find the expressions for the gravitational field \( E \) inside and outside a solid sphere with a mass density that varies as \( \rho = \rho_0 r^2 \), we will follow these steps:

### Step 1: Determine the mass inside the sphere
We start by considering a small spherical shell of radius \( r \) and thickness \( dr \). The volume \( dv \) of this shell is given by:

\[ dv = 4\pi r^2 dr \]
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