Point charge Q1 = 1 nC, Q2 = -2 nC, the Q3 = 1 nC located on the plane in the lattice sites to the cell in the form of a square with sides of 0.1 m. The lattice sites, which are referred to the charges set radius vectors r1 = (a, a), r2 = (0, a), r3 = (- a, a). The remaining nodes are no charges. Determine the strength and potential of the electric field at the point with radius vector r = (2a, 0).

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