ПОМОГИТЕ ПОЖАЛУЙСТА, 20 баллов

By the time mum came home her son had notcooked the dinner.
Who had cooked the dinner by the time mum came home?

Sandra had not been writing a report for three hours before she did not realize it was too late.
Who  had  been writing a report for three hours before she realized it was too late?


This bridge was not built in 1953.
When did this bridge was built?

 
Tom was not reading a very interesting book while his dad was not watching a football match.
Who was reading a very interesting book while his dad was watching a football match?