Say one morning you are considering whether to take a taxi cab or ride a train to work. Both means of transportation would cost you about $4, but you have already paid in advance for the train (since you pay a flat fee at the beginning of the month). If the cab ride would take less time than the train ride, and you are mostly concerned with the time it takes you to get to work (say you have a very important meeting with your boss this morning), the rational decision would be ______