Three charges \( +2q, +3q \) and \( -4q \) are situated at \( (0,-3a) \), \( (2a,0) \), \( (-2a,0) \) respectively in the \( xy \) plane. The resultant dipole moment about origin is ______.
\( 2qa(7\hat{i}-3\hat{j}) \)
\( 2qa(3\hat{i}-7\hat{j}) \)
\( 2qa(3\hat{j}-\hat{i}) \)
\( 2qa(3\hat{j}-7\hat{i}) \)