The electric field E1 at one face of a parallelepiped is uniform over the entire face and is directed out of the face. At the opposite face, the electric field E2 is also uniform over the entire face and is directed into that face (Fig.). The two faces in question are inclined at 30.0° from the horizontal, while E1 and E2 are both horizontal; E1 has a magnitude of 2.50 X l04 N/C, and E2 has a magnitude of7 .00 X l04 N/C.
(a) Assuming that no other electric field lines cross the surfaces of the parallelepiped, determine the net charge contained within.
(b) Is the electric field produced only by the charges within the parallelepiped, or is the field also due to charges outside the parallelepiped? How can you tell?

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