For a circular coil of radius R and N turns carrying current $I$, the magnitude of the magnetic field at a point on its axis at a distance x from its center is given by $B= \large\frac{\mu_0 I R^2N}{2(x^2+R^2)^{3/2}}$ What will be the magnetic field at the center .

Question

$\begin{array}{1 1} \large\frac{\mu_0 I N}{R} \\\large\frac{\mu_0 2I N}{R} \\ \large\frac{\mu_0 I N}{R^2} \\ \large\frac{\mu_0 I N}{2R} \end{array}$