9.28 Eight authors must write a book consisting of 16 chapters. In how many ways can the material be distributed among the authors if two people will write three chapters each, four will write two chapters each, and two will write one chapter each?
9.28 The desired number is:

$$
\begin{aligned}
& C_{16}^{3} \cdot C_{13}^{3} \cdot C_{10}^{2} \cdot C_{8}^{2} \cdot C_{6}^{2} \cdot C_{4}^{2} \cdot C_{2}^{1}= \\
& =\frac{16!}{3!13!} \cdot \frac{13!}{3!10!} \cdot \frac{10!}{2!8!} \cdot \frac{8!}{2!6!} \cdot \frac{6!}{2!4!} \cdot \frac{4!}{2!2!} \cdot 2=\frac{16!}{2^{6} \cdot 3^{2}}
\end{aligned}
$$

Answer: $\frac{16!}{2^{6} \cdot 3^{2}}$ ways.