Chapter 23, Problem 20EAP

You've hung two very large sheets of plastic facing each other with distance d between them, as shown in FIGURE EX23.20. By rubbing them with wool and silk, you've managed to give one sheet a uniform surface charge density ${\eta }_i=-{\eta }_0$ and the other a uniform surface charge density ${\eta }_2=+3{\eta }_0.$ What are the electric field vectors at points l, 2, and 3?