AP Physics C 2020 EM sample exam problem 1e

The sample exam can be found at

[nicholasjanssen]

Wouldn't rho just be the Qenc divided by the volume?

[VigilTheProtogen]

I was thinking use derivative of Qenc with respect to r to get surface charge density at given r. That would yield [4(pi)(r^2)(e0)E]' which becomes 8(pi)(r)(e0)E. But maybe that is not "charge density of sphere at given r"? Very confusing practice problem imo