$\left.\begin{array}{l}{\left[\begin{array}{l}\text { Ratio of volumes }\end{array}\right]} \\ {[\text { Volume of tetrahedron and pyramid }]}\end{array}\right]$

The volume of the tetrahedron $A B C D$ is $V$. Points $M$ and $N$ are taken on edge $A B$, and points $P$ and $Q$ are taken on edge $C D$. It is known that $M N=\alpha A B, P Q=\beta C D$. Find the volume of the tetrahedron $M N P Q$.