Say one morning you are considering whether to take UBER or riding the train to work. Both mediums 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 UBER would take slightly less time than the train ride, and you are mostly concerned with the time it takes you to get to work, you should: a) take the train since you already paid for it
b) take the UBER
c) be indifferent between either modes of transportation
d) find another way to get to work