We are told the initial conditions:
[tex]E= \frac{kq}{d^2} [/tex]
If we were to modify this equation and substitute 1/2d into d, we get:
[tex]E = \frac{k*q}{(0.5d)^2} [/tex]
Simplifying this we get:
[tex]E = 4[ \frac{kq}{d^2} ][/tex]
This is 4 times our initial condition, so the answer is:
4E
Hope this helps!
