问题如下：
There are 15 students in a race of the sports. the winners will be awarded the $100, 50$, and $10. How many different ways do they have?
选项：
A.45.
B.2730
C.455.
解释：
B is correct.
In this case, the order is important, we use the permutation formula to solve this problem.
请问为什么这个是有顺序的呢，金额的大小顺序吗还是？
