First of all, to correct it, the transaction fee for copper is n/10000 of the transaction amount, which should be three/10000 according to the landlord's meaning.

Money used for buying and selling a copper futures contract: 80,000 * 5 (ton/hand) *15% = 60,000 yuan.

Transaction fee: 80000*5*0.0003*2 (bilateral levy) =240 yuan.

Minimum fluctuation unit of copper: 10 yuan/ton.

1 hand The profit and loss calculated by the minimum fluctuation is: 10*5 (ton/hand) =50 yuan.

Back to the topic: how much can the handling fee be earned back?

240/50=4.8 is about 5.

In other words, the minimum profit of five minimum fluctuation units (namely 50 yuan) can earn back the handling fee.

(The above calculation method is approximate, because the closing fee will change after the price rises or falls. )

According to the meaning of the landlord, for example:

Do more than one order: open 80000 positions, close 80050 positions, no loss;

Empty orders: 80,000 positions were opened and 79,950 positions were closed, with no loss.