A Loop carrying current I lies in XY-plane as shown in the figure. The unit vector $\mathrm{k} \wedge$ is coming out of the plane of the paper. The magnetic moment of the current Loop is(a) $\mathrm{Ia}^{2} \mathrm{k} \wedge$
(b) $[(\pi / 2)+1] a^{2} I k \wedge$
(c) $-[(\pi / 2)+1] \mathrm{a}^{2} \mathrm{Ik} \wedge$
(d) $(2 \pi+1) a^{2} I k \wedge$