Scalar product with a unit normal vector

Let $\tvec{a} = \tvec{i} + \tvec{j}$, $\tvec{b} = \tvec{i} - \tvec{j}$ and $\tvec{c} = \tvec{i} + 2\tvec{j} + 3\tvec{k}$.

If $\tvec{n}$ is a unit vector such that $\tvec{a}.\tvec{n} = 0$ and $\tvec{b}.\tvec{n} = 0$, then $|\tvec{c}.\tvec{n}|$ is equal to