Three particles, each of mass m gram, are situated at the vertices of an equilateral triangle ABC of side l cm. (as shown in the figure). The moment of inertia of the system about a line AX perpendicular to AB and in the plane of ABC, in gram$\; cm ^2$ units will be :- <br>

Question

( A ) $\frac{5}{4}ml^{2}$
( B ) $\frac{3}{4}ml^{2}$
( C ) $\frac{3}{2}ml^{2}$
( D ) ${2}ml^{2}$