B_X and B_Y are the magnetic fields at the centre of two coils X and Y respectively each carrying equal current. If coil X has 200 turns and 20 cm…

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