Laila drives to the station each day to pick up her husband Majnu, who usually arrives on a train at 6o’clock. Last Monday, Majnu finished work earlier, caught an earlier train and arrived at the station at 5 ‘o clock. He started to walk home and eventually met Laila who drove him the rest of the way, getting home 20 minutes earlier than usual. On Tuesday, he again finished early and found himself at the station at 5:30. Again he began to walk home, again he met Laila on the way, and she drove him home the rest of the way, Assume constant speed throughout with no wasted time for waiting, backing of the car etc. How earlier than the usual time were they home on Tuesday?