Electric field in a region is given by
\[
\vec{E} = A x\,\hat{i} + B y\,\hat{j},
\]
where \( A = 10 \,\text{V/m}^2 \) and \( B = 5 \,\text{V/m}^2 \). If the electric potential at a point \( (10, 20) \) is \(500\ \text{V}\), then the electric potential at origin is __________ V.
