A very long thick plate has uniform positive volume charge density given by $\rho \left(x\right)={\rho }_0 \mathrm{for} -\frac{d}{2}\le x\le \frac{d}{2}$, where ρ ₀ is a positive constant, d is the thickness of the plate and x = 0 is the centre of the plate.

114. Use Gauss' law of find E(a)
(1) ρ ₀ a/ε ₀                    (2) 2ρ ₀ a/ ε ₀                          (3) ρ ₀ a/2ε ₀                  (4) 4ρ ₀ a/ε ₀