Two long straight parallel wires are a distance $2 \mathrm{d}$ apart. They carry steady equal currents flowing out of the plane of the paper. The variation of magnetic field $B$ along the line $xx$ ' is given by

The magnetic field at the centre ${}^{\text{'}}O^{\text{'}}$ in the given figure is

The ratio of the magnetic field at the centre of a current-carrying circular coil to magnetic moment is $x$. If the current and the radius both are doubled. The new ratio will become