8.5. In the tetrahedron $K L M N$, the lengths of the edges are known: $K L = M N = 9$, $K M = L N = 15$, $K N = L M = 16$. Points $P, Q, R, S$ are the centers of the circles inscribed in triangles $K L M$, $K L N$, $K M N$, and $L M N$. Find the volume of the tetrahedron $P Q R S$. Round the answer to the nearest hundredth if necessary.
Answer: 4.85 (exact value: $\frac{11 \sqrt{7}}{6}$ ).