While carrying out an experiment you watch an electrically charged microscopic drop of oil (mass 5.68 micrograms, diameter 0.48 mm and electric charge of -96e) that is slowly falling vertically in an evacuated chamber toward a small flat, electrically charged surface. After a while you notice that the drop comes to a stop and remains suspended motionless, 3.50 mm above the flat surface. What is the minimum amount of charge that should be on the flat surface? Suppose that the drop and the charged flat surface might be considered to be point charges and as the drop falls it (the drop) does not gain or lose any electrical charge or mass. Also, suppose that at the location where you are the acceleration due to gravity is 9.83 m/