Magnetics

\(\mathrm{B}_{X}\) and \(\mathrm{B}_{\mathrm{Y}}\) are the magnetic fields at the centre of two coils \(\mathrm{X}\) and \(\mathrm{Y}\) respectively each carrying equal current. If coil \(X\) has 200 turns and \(20 \mathrm{~cm}\) radius and coil \(Y\) has 400 turns and \(20 \mathrm{~cm}\) radius, the ratio of \(B_{X}\) and \(B_{Y}\) is :