The electric field in a region is given by $\overrightarrow{\mathrm{E}}=(\mathrm{Ax}+\mathrm{B})\hat{\mathrm{i}}$, where E is in ${\mathrm{NC}}^{-1}$ and x is in metres. The value of constants are A = 20 SI unit and B = 10 SI unit.  If the potential at x = 1 is V₁ and that at x = -5 is V₂, then ${\mathrm{V}}_1-{\mathrm{V}}_2$ is