Mary与Bill不期而遇，邀请他一起吃晚饭。但Bill当晚7点要去北京，下周一回来。Mary让Bill回来后给她打电话。

(Mary: M; Bill: B)

M: Bill,is that you I haven’t seen you for a long time.

B: Hi, Mary. Great to see you again. 51__________

M: Fine. Why don’t we get together and have a chat How about 52__________this evening？

B:Well, it sounds great, but I’m 53__________ at 7 o’clock.

M:What a pity!

B:Well, I’ll be back 54__________. We can find a time to meet again.

M:Okay. 55__________when you are back.

B:No problem. Goodbye!

M:Bye!