The electric field intensity generated by a single point charge is given by
[tex] E(r)=k\frac{q}{r^2} [/tex]
where
k is the Coulomb's constant
q is the charge
r is the distance from the charge
In this problem, the charge is [tex] q=25 \mu C=25 \cdot 10^{-6} C [/tex] and we are asked to calculate the field at distance [tex] r=9.0 m [/tex], so the electric field is
[tex] E(9.0 m)=(8.99 \cdot 10^9 Nm^2C^{-2})\frac{25 \cdot 10^{-6} C}{(9 m)^2}=2775 V/m [/tex]
