Find the position vector of a point $R$ which divides the line joining two points $P$ and $Q$ whose position vectors are $ \hat i + 2\hat j − \hat k$ and $– \hat i + \hat j + \hat k$ respectively, in the ratio $2 : 1$ externally

Question

$\begin{array}{1 1}(A) \hat i+2\hat j+\hat k \\(B) \large\frac{\hat i-2\hat j+\hat k}{3} \\ (C) -3\hat i+3\hat k \\ (D) \hat i-2\hat j-\hat k \end{array} $