Say I spend 200 foreign currency on Jan 1.
300 foreign currency on April 1.
What exchange rate shall I use for my book-keeping? The exchange rate on Jan1 for 200 and April 1 for 300 ? Or use the year end Dec 31 exchange rate for all 500 ?
Also each back offers different exchange rate, say BOA and Citi might offer different rates. Which bank rate shall I use ?