65. Two parallel infinite plane oppositely charged with unequal densities modulo + σ1 and -σ2. Abscissas indicated in Figure 1 points are: x = -3 m, x = -1 m,
x = +2 m, x = 3 m. The potential difference between points 1 and 2 is equal to φ - φ = 400 V a) Which of the densities (+ σ or -σ) larger in absolute value? b) What is the potential difference φ -φ?