3. Thirteen millionaires arrived at the economic forum and settled in the "Super Luxury+" hotel. The hotel has rooms of 3 different types: 6-star, 7-star, and 8-star. The millionaires need to be accommodated in such a way that all three types of rooms are used (i.e., at least one person must be placed in a 6-star room, at least one in a 7-star room, and at least one in an 8-star room). Additionally, a richer millionaire cannot be placed in a room with fewer stars than a less wealthy one.

In how many ways can they be accommodated (all millionaires have different wealth levels)?
Answer: $C_{12}^{2}=66$.