In a region electric field is given by E =4 x i N / C. The potential difference between points A (x=1 m ) and B (x=3 m ),( V_A - V_B ) is

In a region electric field is given by $\displaystyle \overrightarrow{\mathrm{E}}=4 x \hat{\mathrm{i}} \mathrm{N} / \mathrm{C}$. The potential difference between points $\displaystyle \mathrm{A}(x=1 \mathrm{~m})$ and $\displaystyle \mathrm{B}(x=3 \mathrm{~m}),\left(\mathrm{V}_{\mathrm{A}}-\mathrm{V}_{\mathrm{B}}\right)$ is