Earth's lower atmosphere contains negative and positive ions that are produced by radioactive elements in the soil and cosmic rays from space. In a certain region, the atmospheric electric field strength is 158 V/m and the field is directed vertically down. This field causes singly charged positive ions, at a density of 680 cm, to drift downward and singly charged negative ions, at a density of 639 cm, to drift upward (see the figure). The measured conductivity of the air in that region is 3.72 x 10-14 (Q-m). Calculate (a) the magnitude of the current density and (b) the ion drift speed, assumed to be the same for positive and negative ions. (a) Number Units (b) Number Units