Look at the attached problem with solutions. I don't understand what the author means in c) when he says that succesive shells contribute less and less because the cross sectional area grows proportional to r2. The flux through a closed surface is always the same (Gauss' law). Rather the reason why the b becomes negligible is in my opionion that you are very far away from the shell. Can anyone explain what the author means by this "succesive shells contribute less and less"?