A thin ring of radius R meter has charge q coulomb uniformly spread on it. The ring rotates about its axis with a constant frequency of f revolutions/s. The value of magnetic induction in $Wb/m^2$ at the centre of the ring is –

Question

( A ) $\frac{\mu_0qf}{2\pi R}$
( B ) $\frac{\mu_0q}{2 f R}$
( C ) $\frac{\mu_0qf}{2R}$
( D ) $\frac{\mu_0q}{2\pi f R}$