Solve:


62. A thin infinite non-conducting plate is in the XOY plane. It has a circular hole of radius R with center at the origin. The plate has a uniform surface charge density $\sigma$ on its upper surface. Find the electric field at point (0, 0, z). 


$\left(A\right) \frac{\sigma z}{2{\epsilon }_0\sqrt{R^2+z^2}} \left(B\right) \frac{\sigma R}{2{\epsilon }_0\sqrt{R^2+z^2}} \left(C\right) \frac{\sigma z}{{\epsilon }_0\sqrt{R^2+z^2}} \left(D\right) \frac{\sigma R}{{\epsilon }_0\sqrt{R^2+z^2}}$