Shanghai Futures Exchange Aluminum: The daily maximum price fluctuation limit shall not exceed 5% of the previous settlement price.

If the settlement price is 15000 yuan/ton, then:

15000× (1+5%) =15750 yuan.

That is, the highest price can be sold to 15750 yuan.

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That depends on what year your topic is. The latest regulation is that the daily limit of Shanghai aluminum futures is 5%. It seems to have been 4% before. You can log on to the website of Shanghai Futures Exchange.