Two point charges of magnitudes $\mathbf { 1 } \boldsymbol { \mu C }$ and $\mathbf { 2 } \boldsymbol { \mu C }$ are placed at two vertices of an equilateral triangle of side $\mathbf { 3 ~ c m }$. Another charge of $\mathbf { 3 ~ } \boldsymbol { \mu } \mathbf { C }$ is brought from infinity to the third vertex of the triangle. Find the work done in bringing the charge to the third vertex.
(A) 0.9 J
(B) 1.8 J
(C) 4.5 J
(D) 2.7 J