9. (12 points) Four friends want to subscribe to a “Family Package”, which allows them to send text messages to each other for free after paying a certain amount of money. However, the awkward thing is that the local options are only a 10 yuan “three-person free” Package A and a 5 yuan “two-person free” Package B. The four friends thought about it and decided they could subscribe to several of these packages so that they can all send free messages to each other through intermediaries. In the case of spending the least amount of money, they have $\qquad$ ways to subscribe to the packages.
【Analysis】If 4 people want to send text messages to each other for free, they need to spend at least 15 yuan. They can subscribe to 1 three-person package and 1 two-person package, or 3 two-person packages. By categorizing and discussing, and using the principle of counting, we can draw a conclusion.

【Solution】Solution: If 4 people want to send text messages to each other for free, they need to spend at least 15 yuan. They can subscribe to 1 three-person package and 1 two-person package, or 3 two-person packages. In the first case, subscribing to 1 three-person package and 1 two-person package, there are 4 ways to choose 3 people out of 4 to subscribe to the package, and 3 ways to choose 1 person from the 3 to subscribe to the two-person package with the one who did not subscribe to the three-person package. Therefore, there are $4 \times 3=12$ ways in total;

In the second case, subscribing to 3 two-person packages, $A$ and $B$, $B$ and $C$, $C$ and $D$, there are $4 \times 3 \times 2 \times 1 \div 2=12$ ways in total;

In the third case, subscribing to 3 two-person packages, $A$ and $B$, $C$, $D$, there are 4 ways in total.
In summary, there are $12+12+4=28$ ways in total.
Therefore, the answer is 28.