Five hundred dollars, please. And could you give me ten dollar in small change?
请换500美元。再另外能否给我10元的小面额零钱?
He is a doctor. He has his own practice.
他是个医生,他自己开业。
Some of the bigger firms are engaged in researches which are of such general and fundamental nature that it is a positive advantage to them not to keep them secret.