three concentric metallic spherical shell A,B and C or radii a,b and c(a

Three concentric spherical metallic shells A, B and C of radii of a,b and c (c>b>a) have charge densities σ, -σ and σ respectively. The potential of shell B isOptions:
1. (a+b+c) σ/ε0

2. (a2/b-b+c) σ/ε0

3. (a2/c-b2/c+c) σ/ε0

4. σc/ε0

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