Erase all the cavities!

Inside a ball charged uniformly with volume density $\rho =4 \text{ C/m}^{ 3 }$ of radius, $R=1 \text{ m}$ , there are 5 spherical cavities of radii $r=10 \text{ cm}$ . The center of each cavity is displaced with respect to the center by a distance $a=50 \text{ cm}$ . Find the sum of magnitudes of electric field strengths inside the cavities, assuming permittivity equal to 1.

The answer is of the form $\frac { a }{ b{ \varepsilon }_{ 0 } }$

Find: $a+b$

Note : There is no point of intersection between the cavities.

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