You can find out Mastercard currency exchange rates on the official websites of these payment systems. Keep in mind that the Canada USD MC card vendor will add a 3,50% currency exchange fee to the exchange rate.

Important: Transactions foreign currencies are settled by Mastercard within 2-3 days. The transaction has two stages: funds are first held (pre-authorization) and then debited. In this case, the debit is made at the current exchange rate, not at the rate of the original payment day. If the exchange rate changes while the transaction is being processed, the debited amount will be different from the amount originally held.