3.22. The volume of the parallelepiped $A B C D A_{1} B_{1} C_{1} D_{1}$ is $V$. Find the volume of the common part of the tetrahedra $A B_{1} C D_{1}$ and $A_{1} B C_{1} D$.
3.22. The common part of the specified tetrahedra is a convex polyhedron with vertices at the centers of the faces of the parallelepiped. A plane equidistant from two opposite faces of the parallelepiped divides this polyhedron into two quadrilateral pyramids, the volume of each of which is equal to $V / 12$.