Orthogonal System of Vectors

Q. The unit vector in the direction of sum of the vectors $\overrightarrow{A}=2\hat{i}+4\hat{j}-7\hat{k}$ and $\overrightarrow{B}=4\hat{i}-6\hat{j}+4\hat{k}$ will be

1. $6\hat{i}-2\hat{j}-3\hat{k}$
2. $\hat{i}-\hat{j}-\hat{k}$
3. $\frac{6\hat{i}-2\hat{j}-3\hat{k}}{7}$