1. A co-worker(...)several days.
Interpretation 1: The co-worker handles a convenience relationship with the manager, and probably is taking information about other partners opinions to inform this one.
Interpretation 2: The co-worker is a member of conflict resolution committee and is putting together the information in order to establish a dialogue which can make solution to the disagreements.
2. You´ve requested(...)to help.
Interpretation 1: The teacher has an conflict of interests with the student and simply does not like him and rejects intentionally to help him.
Interpretation 2: The teacher is busy with the exams and activities which has to check and evaluate; however she tried to establish extra class meetings in order to help to make lessons clearer.
The correct answer in this case is "we"
Us is also correct but in that case the sentence would not be an elliptical one. If you use "we" then the sentence is both correct and elliptical which fits the description of the question.
