1) Yuri had been working on his computer for two hours

1) Yuri had been working on his computer for two hours before it broke down.
2) I was mopping the floor while my brother was cutting the grass.
3) Were you sleeping when the earthquake started?
4) This time last week, I was flying to Paris.
5) Sam was really happy because he had passed all his exams.
6) Sarah had cleaned the house by the time her barents came back.
7) James had waited for a while and then opened the door to see who was making that strange noise.
8) Marion didn't go shopping because she spent the morning with her little brother that day. Помогите определить время у каждого предложения.