Electrostats, Gauss Theorem qusetion: Struck in middle

[PrashntS]

1. The question is to find the volume charge density. Given is non uniform, but spherically symmetric electric field, E=K.r⁴, K being a constant. Original question can be viewed in image:

* Question no. 53

Homework Equations

Answer is: ρ=6Kr³ε

The Attempt at a Solution

Tried solving so many times. Once, I got half the answer I should have got!
Solution steps are attached.:

I got struck at the last equation,:
4Kεπr⁶=∫ ρ.dV

 

[Dr_Stirk]

Use gauss law in differential rather than integral form. 1/r^2*d/dr(r^2*E)=rho/epsilon