第1个回答 2012-09-03
It is my pleasure(或者直接My pleasure,比较常用). Any problem please don't hesitate to contact me.
我经常这么回复的。
第2个回答 2012-09-03
You are welcome! Please feel free to inform me if you have any further questions.
第3个回答 2012-09-03
You're welcome and contact me whenever you have questions.