9. (5 points) Place 11 balls into three boxes so that the number of balls in each box is different. Then, the box with the most balls can contain at most $\qquad$ balls, and must contain at least $\qquad$ balls.
【Analysis】To ensure each box has balls and the number of balls in each box is different, at least one box should have 1 ball, the second box should have 2 balls, and at this point, the third box will have the most balls. By calculating $11-1-2$, we can find the solution.

【Solution】Solution: $11-1-2=8$ (balls),
Answer: When 11 balls are placed in three boxes, ensuring the number of balls in each box is different, the box with the most balls can have a maximum of 8 balls. If the goal is to minimize the number of balls in the box with the most, the numbers should be as close as possible, such as $2,3,4$, which can accommodate 11 balls, and the box with the most balls will have at least 5 balls. Therefore, the answers are: 8,5.