present perfect with for and since (2)

Choose the correct answer.

1. She's had a pilot's licence forsince six months.
2. He hasn't done any work since two daysfor three hours.
3. Tony and Ben have been in Mr Ali's office sincefor10 o'clock.
4. We haven't seen Madga sinceMadga since seenthe end of term party.
5. This room hasn't been cleaned since a weeksince last week.
6. Have you worked here forsincea long time?