Theoretically, foreign exchange is not only used to buy related equipment and materials, but also used to pay the wages of workers and managers in the country where the contractor is located, and to pay management fees to the headquarters. Exchange gains and losses of the foreign currency part of purchased materials and equipment (no matter what currency unit is selected) can be made up by adjusting the material price, so there is no need to consider the gains and losses.

The relationship between wages and the currency where the headquarters management fee is paid and the foreign currency stipulated in the tender documents is very important. Therefore, bidders need to compare the relationship between the two currencies and choose the currency that is beneficial to the contractor. The second step is to determine the proportional relationship between local currency and foreign currency. After determining the foreign currency, the bidder shall determine the relationship between local currency and foreign currency according to the proportion of funds used in the bidding scheme, that is, to estimate the proportion of local currency and local currency required by the project.