Just show you the formula. E 1-E2 = e1(r 1-R2)/360 * l, e1,E2 represents the exchange rate for early delivery and the exchange rate for normal delivery respectively, and r1,R2 represents the different returns (i.e. interest rates) of the two currencies respectively.

360/ days in advance = time period for early delivery (corresponding to the interest rate based on one year). This formula is actually very easy to understand. If both parties are multiplied by the transaction amount of M at the same time, the left side indicates the gains and losses caused by the exchange rate difference (easy to teach in advance), and the right side indicates that if there is no transaction denominated in two currencies, the gains corresponding to the lead time should be equal on both sides.

Ps: Answer the question for the first time. If you don't know, call me.