일반물리학 2 — Gauss' Law: Problem 30

30 In Fig. 23-37, a butterfly net is in a uniform electric field of magnitude $E = 4.5 \text{ mN/C}$. The rim, a circle of radius $a = 11 \text{ cm}$, is aligned perpendicular to the field. The net contains no net charge. Find the electric flux through the netting.