일반물리학 2 — Gauss' Law: Problem 22

22 A charged particle is held at the center of a spherical shell. Figure 23-33 gives the magnitude $E$ of the electric field versus radial distance $r$. The scale of the vertical axis is set by $E_s = 5.0 \times 10^7 \text{ N/C}$. Approximately, what is the net charge on the shell?