If vectors a = 2i + 3j - k and b = i - 2j + 3k, then |a × b| is:

$$\vec{a} \times \vec{b} = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ 2 & 3 & -1 \\ 1 & -2 & 3 \end{vmatrix}$$

$$= \hat{i}(9 - 2) - \hat{j}(6 + 1) + \hat{k}(-4 - 3)$$

$$= 7\hat{i} - 7\hat{j} - 7\hat{k}$$

$$|\vec{a} \times \vec{b}| = \sqrt{49 + 49 + 49} = 7\sqrt{3} \approx \sqrt{147}$$

Hmm, none match exactly. Rechecking: $\sqrt{99} \approx 9.95$, $7\sqrt{3} \approx 12.12$. The answer is $\sqrt{147}$ but closest listed is $\sqrt{155}$.