The copper price is 48,000 yuan. If you buy five tons, your deposit is 24,000 yuan (48,000× 5/10 = 24,000).
Well, the upper limit of copper increase is 5%, that is to say, it will rise to 50400 at most, and you can earn (50400-48000) × 5 = 12000 at most.
Similarly, if the upper limit of reduction is 5%, your loss will be 12000 yuan.
According to this algorithm, you can earn at most 12000/24000 = 50% a day. Is it crazy to compare with stocks?
Therefore, a general increase of more than 2% is considered as a very serious increase.