A man I know, who lives in my neighbourhood, travels to Chinsura every day for his work. His wife drives him over to Howrah Station every morning and in the evening exactly at six PM she picks him up back at the station and takes him home. One day he was let off at work an hour earlier, and so he arrived at the Howrah Station at five PM instead of at six. He started walking home. However he met his wife enroute to the station and got into the car. They drove home arriving ten minutes earlier than usual. How long did the man have to walk, before he was picked up by his wife?