The magnetic field at the centre of an equilateral triangular loop of side $2L$ carrying a current $i$ is

Question

$\begin {array} {1 1} (a)\;\large\frac{9\mu_0i}{4 \pi L} & \quad (b)\;\large\frac{\mu_0i}{ \pi L} \\ (c)\;\large\frac{3\mu_0i}{4 \pi L} & \quad (d)\;\large\frac{\mu_0i}{2 \pi L} \end {array}$