In crystals of the salt cesium chloride, cesium ions cs+ form the eight corners of a cube and a chlorine ion cl- is at the cube's center (see the figure). the edge length of the cube is l = 0.46 nm. the cs+ ions are each deficient by one electron (and thus each has a charge of +e), and the cl- ion has one excess electron (and thus has a charge of -e). (a) what is the magnitude of the net electrostatic force exerted on the cl- ion by the eight cs+ ions at the corners of the cube? (b) if one of the cs+ ions is missing, the crystal is said to have a defect; what is the magnitude of the net electrostatic force exerted on the cl- ion by the seven remaining cs+ ions?