Ответ:
It (1) was a rainy afternoon.
Nick (2) was sitting at the table and (3) writing to his friend.
He was writing about his last summer holidays.
His mother (5) was cooking dinner when he (6) was writing the letter.
As soon as the dinner (7) was ready, mother (8) invited him to have dinner. Nick (9) stoped writing and (10) went to the kitchen.