Arun drives to the bus stop everyday to pick up his girlfriend such that he reaches the bus-stop at 4pm . One day his girlfriend arrived at the bus stop at 3pm and started walking towards the home. Arun picked her up in between and together they reached home 20 minutes early. Another day,she reached the bus-stop at 3:30 pm and started walking towards home and Arun picked her up in between. How early would they reach home?