5. We are an authorized foreign exchange bank and can change them for you.
我们是指定经营外汇业务的银行，可以为您兑换。
还能这样说：
We are designed to manage foreign currency business. We can handle the service.
We are the bank designated to handle foreign exchange, so we can change foreign currency for you.
应用解析：
go foreign 驶向外国；在从事对外贸易的船上当船员；
sell foreign 卖给外国人；
foreign to 和……无关的；不适合于……
6. What kind of currency do you want?
您要哪种货币？
还能这样说：
In what denominations?
Which kind of foreign currency do you change?
谚语：
Do not forget little kindness and do not remember small fault.
小善不忘，不错不念。
7. Five-Yuan notes would be better.
最好是5元面值。
还能这样说：
It's better to change into five-Yuan notes.
In five, please.
应用解析：
back a note 签名于票据背面；
change one's note 改变态度；
compare notes 交换意见；对笔记；
account note 账单；
advance note 预付票据
8. Today's exchange rate of RMB to USD is 698 RMB Yuan equal to 100 US dollars.
今天的汇率是698元人民币兑换100美元。
还能这样说：
According to today's rate, one dollar is equal to 6.98 Yuan.
It's 1 US dollar to 6.98 RMB.
应用解析：
be equal to 等于；有……的能力；胜任；
be the equal to one's word 说到做到；
be without equal 无比，无敌