In one university that I worked at, there was a mail room on every single floor.

在我工作的一所大学里，每层楼都有一个收发室。

Unfortunately, you don't have a floor plan, and you'll only have enough time to search a single floor before the alarm system reactivates.

不幸的是，您没有平面图，而且您只有足够的时间在警报系统重新激活之前搜索一个楼层。