So our favourite couple, Alice and Bob finally decided to get married ;)
Bob was already working in a well reputed company as Information Security Analyst. Alice, used to get bored at home, so she decided to be a chef. Both were happy, it all worked out well.
On weekdays, Bob's routine is:
Bob wakes up at 8, eats lovely and healthy breakfast prepared by Alice, goes to his office (which is nearby their home). He works hard all the day (as his work is highly confidential, we don't know much).
Bob arrives at the metro station from work at 9 pm. Alice leaves home in her car to meet him there at exactly 9 pm, and drives him home.
On one fine Friday, Bob got to the station an hour early, and started walking home, until Alice met him on the road. They got home 20 minutes earlier than usual.
The questions is: For how many minutes, was he walking?
All the speeds are constant!