Vector Algebra

Let $2 \hat{\mathbf{i}}-\hat{\mathbf{j}}-\hat{\mathbf{k}}, 5 \hat{\mathbf{i}}+\hat{\mathbf{j}}-2 \hat{\mathbf{k}},-13 \hat{\mathbf{i}}-11 \hat{\mathbf{j}}+4 \hat{\mathbf{k}}$ be the position vectors of three points. $A, B$ and $C$, respectively. If $\mathbf{A B}=\lambda \mathbf{B C}$ and $\mathbf{A C}=\mu \mathbf{C B}$, then $\lambda+\mu=$