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