За правильность надбавлю make up as many sentences as you can using a) past indefinite or past perfect: 1. он вернулся at 6 o'clock by 6 o'clock on saturday by monday at that time 2. я закончил работу by that time before you came while you were away b) future indefinite or future perfect: 1. он вернется at 6 o'clock by 6 o'clock on saturday by monday 2. я закончу работу at that time by that time before you come while you are away