$(a)\;\large\frac{u}{12} (\normalsize \hat{i}+\normalsize \sqrt{3}\hat{j})\qquad(b)\;\large\frac{u}{12} (\normalsize \hat{i}-\normalsize \sqrt{3}\hat{j})\qquad(c)\;\large\frac{u}{12} (-\normalsize \hat{i}+\normalsize \sqrt{3}\hat{j})\qquad(d)\;\large\frac{u}{12} (-\normalsize \hat{i}-\normalsize \sqrt{3}\hat{j})$