At each point on the surface of the cube shown in Fig. 23-27, the electric field is parallel to the z axis. The length of each edge of the cube is 3.2 m. On the top face of the cube the electric field is in the negative z direction and has a magnitude of 38 N/C magnitude. On the bottom face of the cube the field is in the positive z direction and has a magnitude of 23 N/C. Determine the net charge (in nC) contained within the cube.