Is Electric Flux Undefined with Surface Charges on a Sphere?

[lugita15]

Homework Statement

This was on the 1982 AP Physics C E&M Free Response

Homework Equations

Electric flux through a closed surface = (Charge enclosed)/epsilon_0

The Attempt at a Solution

This is the official solution given:

I believe, however, that the electric flux must be undefined. The electric flux is the integral of E.dA. But since there are charges *on* (as opposed to inside) two of the points on the sphere, E at those points would be infinite. Thus, integral E.dA would be undefined.

Any help would be greatly appreciated.
Thank You in Advance.

 

[Doc Al]

I think you have misread the question. The radius of the sphere is 2a, not a.