Q.7). A point charge 25$\mu C$ is located in the XY plane at the point of position vector $\overrightarrow{r_0}=\left(\hat{i}+\hat{j}\right)m$. What is the magnitude of electric field at the point of position vector $\overrightarrow{r_1}=\left(4\hat{i}+5\hat{j}\right)m$?
(A) $900\frac{V}{m}$
(B) $9\frac{kV}{m}$
(C) $90\frac{V}{m}$
(D) can't be determined