Every day, John takes the train to travel from his work back to Mexico City, his place of residence. Usually, he arrives at the station of Mexico at six o’clock, and exactly at that moment, his wife picks him up by car. Yesterday evening, John took an earlier train, without informing his wife, and therefore he already was at the station of Mexico at five o’clock. He decided to walk part of the way to meet his wife. When he met the car with his wife, he drove home with her. In this way, they were home ten minutes earlier than normal. John’s wife always drives the entire way between home and station at the same constant speed.
How long did John walk yesterday evening?