The Neutron-to-Proton Ratio. Hope this helps Sorry if it's wrong I'm a little rusty on Physics.
Answer:
The permittivity of rubber is 
Explanation:
From the question we are told that
The magnitude of the point charge is 
The diameter of the rubber shell is 
The Electric field inside the rubber shell is 
The radius of the rubber is mathematically evaluated as

Generally the electric field for a point is in an insulator(rubber) is mathematically represented as
Where
is the permittivity of rubber
=> 
=> 
substituting values


i do believe the answer is c not sure but correct me if im wrong
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