澳洲幣點計?

買澳洲幣 50,000 at exchange rate of AUD1 = HK$5
=> AUD50,000 = HK$250,000

賣出澳洲幣 50,000 at exchange rate of AUD1 = HK$5.5
=> AUD50,000 = HK$275,000

Your earning = HK$275,000 - HK$250,000 = HK$250,000
Your earning = The amount of HKD when you sell AUD - The amount of HKD when you buy AUD

2009-03-04 13:52:32 補充：
Sorry Typing mistake, it should be Your earning = HK$25,000, not HK$250,000