Solution (source code)

= Solution

The <volume> of a <parallelepiped> is the absolute <scalar triple product> of its three edge <vectors>. Since $\overrightarrow{OP}\times\overrightarrow{OQ}=(0,0,3)$,
$$
\boxed{\mathcal V=\left|\bigl(\overrightarrow{OP}\times\overrightarrow{OQ}\bigr)
\cdot\overrightarrow{OR}\right|=3}.
$$
The factor $1/6$ appropriate to a <tetrahedron> must not be applied to this parallelepiped.