If $\overrightarrow u=\hat i+\hat j,\:\overrightarrow v=\hat i-\hat j\:and\:\overrightarrow w=\hat i+2\hat j+3\hat k$ and $\overrightarrow n$ is a unit vector such that $\overrightarrow n.\overrightarrow u=\overrightarrow n.\overrightarrow v=0$, then $|\overrightarrow n.\overrightarrow w|=?$

Question

$(a)\:\:o\:\:\:\qquad\:\:(b)\:\:1\:\:\:\qquad\:\:(c)\:\:2\:\:\:\qquad\:\:(d)\:\:3$