#4: In the lower atmosphere of the Earth there are negative and positive ions, created by radioactive elements in the soil and cosmic rays from space. Suppose that at a certain time in a certain region, the atmospheric electric field strength is 1120 V/m, directed vertically down. Due to this field, singly charged positive ions, 8600 per cm3, drift downward and singly charged negative ions, 1650 per cm3, drift upward. The measured conductivity is 5 .70 x 10-14(ohms-m) . Calculate the ion drift speed, assumed the same speed for positive and negative ions. Put your answer in the form of "a.bc x 10^ " m/s