A large number of positive charges each of magnitude $$q$$ are placed along the $$X$$-axis at the origin and at every 1 cm distance in both the directions. The electric flux through a spherical surface of radius 2.5 cm centred at the origin is

The electric field in a region of space is given as $$\mathbf{E}=\left(5 \mathrm{NC}^{-1}\right) x \hat{i}$$. Consider point $$A$$ on the $$Y$$-axis at $$y=5 \mathrm{~m}$$ and point $$B$$ on the $$X$$-axis at $$x=2 \mathrm{~m}$$. If the potentials at points $$A$$ and $$B$$ are $$V_A$$ and $$V_B$$ respectively, then $$\left(V_B-V_A\right)$$ is