question_answer

If the lines \[\vec{r}=-\hat{i}+\hat{j}-\hat{k}+\lambda (2\hat{i}+\hat{j}+3\hat{k})\] and \[\vec{r}=-2\hat{i}+\alpha \hat{j}+\hat{k}+,\mu (2\hat{i}+3\hat{j}+4\hat{k})\] \[(\lambda ,\mu \in R)\] are coplanar, then the value of \[\alpha \] is

A) \[\frac{-9}{2}\]                                                 

B) \[\frac{11}{2}\]

C) \[\frac{-11}{2}\]                               

D) \[\frac{15}{2}\]