A 2 mm-diameter plastic bead is charged to -1 nC. An electron is fired at the bead from far away. It approaches the bead, stops, turns around, and moves away as if "reflected" off the bead. The mass of an electron is 9.11 x 10-31 kg. To get the electron up to speed we accelerate it between two parallel plates with a 10 V potential difference. The 'tes are 10 cm square and 2 mm apart. If the field in the previous question were 2500 N/C (it's not) what would be the charge on the plates?