https://imgur.com/a/n0iohng
I am using Guru's Electromagneic Theory Fundamentals: https://www.amazon.ca/Electromagnetic-Field-Theory-Fundamentals-Singh/dp/0521116023
For finding the electric field intensity, I am using the equation:
https://imgur.com/a/RHS6SfY
I am unsure about what the value of r prime should be for a solid.