\(E=E_oe^{-\cfrac{x}{a_e}}\)
\(x\) is measured from the surface of the charge, where \(a_e\) is the radius of the charge. So
\(E_oe^{-\cfrac{0}{a_e}}=E_o\)
\(E_o\) is on the surface of the charge.
It is then possible that \(a_e\gt r_e\), as the measurement of \(x\) does not include \(a_e\).
