This topic is related to objects. Of course, we have to start with the real thing, and there are five times and four times. Neither the notebook nor the dancing shoes can be used as prizes, because if the notebook is the third prize, then you can't choose four times that of the second grade. So is dancing shoes. There are two options.

If the third prize is X, it is 5 * 20x+10 * 4x * 25 * X.

The most expensive cost is 990 yuan.