Halliday, Resnick & Walker — Gauss' Law: Problem 8

8 In Fig. 23-25, a small circular hole of radius $R = 1.30\text{ cm}$ has been cut in the middle of an infinite, flat, nonconducting surface that has uniform charge density $\sigma = 4.50\text{ pC/m}^2$. A $z$ axis, with its origin at the hole’s center, is perpendicular to the surface. In unit-vector notation, what is the electric field at point $P$ at $z = 2.56\text{ cm}$? (Hint: See Eq. 22-26 and use superposition.)