urgent

Rashmi leaves office at 6.00Pm and catches a 6.30 pm local train that arrives in her town at 7.00 pm . Her father leaves home to pick up her at 7.00pm from the station as she gets off the train. Yesterday , Rashmi left her office early and took a 6.00 pm train and arrived at 6.30 pm .As her father was not there to pick her up,she started walking towards home. Her father left home at the usual time , saw her daughter walking, picked her up and drove home arriving there 10 mins earlier than usual. For how ling did rashmi walk before her father picked her up?
A]10min b]15 min c]20 min d]25 min

Because the trip is two ways, for each minute the car saves on the way there, it saves on the way back. This means it picks Rashmi up five minutes before 7:00, which would be 6:55, so the answer is D.