d
\({B}=3\left[\frac{\mu_{0} {i}}{4 \pi {r}}\left(\sin 60^{\circ}+\sin 60^{\circ}\right)\right]\)

\(\tan 60^{\circ}=\frac{\ell / 2}{{r}}\)

Where \({r}=\frac{9 \times 10^{-2}}{2 \sqrt{3}} \,{M}\)

\(\therefore {B}=3 \times 10^{-5}\, {T}\)

Current is flowing in clockwise direction so, \(\overrightarrow{{B}}\) is inside plane of triangle by right hand rule.