In a particular region of Earth's atmosphere, the electric field above Earth's surface has been measured to be 140 N/C downward at an altitude of 210 m and 163 N/C downward at an altitude of 360 m. Calculate the volume charge density of the atmosphere, assuming it to be uniform between 210 and 360 m. (Hint: You may neglect the curvature of Earth. Why?) Units should be in C/m3