answer: #Person1# overslept again because #Person1#'s alarm didn't work. #Person2# recommends #Person1# get a new one before #Person2# is fired.
documents: #Person1#: Sorry, I overslept. My alarm clock didn't go off this morning.
  #Person2#: Again?
  #Person1#: That's right, even though I did set the alarm last night.
  #Person2#: Your clock never works. Perhaps you should buy a new one.
  #Person1#: Well. If it breaks down again tomorrow, I'll definitely buy a new one.
  #Person2#: Maybe by then it will be too late.
  #Person1#: What do you mean too late?
  #Person2#: By that time, you will be fired.