Answer:

Step-by-step explanation:
I will use the Gauss's Law to find the field:
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the surface S is a sphere of radio r, the normal vector only has radial coordinates.
E(r)=E(r)r /*The field, based on spherical symmetry, only depends of the radius, and only has radial coordinate*/
if r<a


if a=<r<b



with K=constant