由“there is a flight at 6: 45 and one at 18: 00”可以得出答案。

听力原文：

W: Northwest Airways, good morning. Can I help you?

M: Yes, do you have any flights to Sydney next Tuesday afternoon?

W: Yes, there is a flight at 6: 45 and one at 18: 00.

M: That's fine. Could you tell me how much return flight costs?

W: That would be 418 dollars.