Every day , John Arrives at 5 p.m ,at the station from work.
His wife leaves home in her car .
and reach station at 5 p m exactly to meet him daily .
and drives him home .
One day, John gets to the station an hour early, and starts walking home, until his wife meets him on the road.
They get home 30 minutes earlier than usual .
Question is .
How long (time) was he walking?
( Distances are unspecified. Speeds are unspecified, but constant.)