The gas station on the edge of town has gas that is 30c/gallon cheaper than my local station. I buy 10 gallons of gas a week. Assume that I value my time at $10 per hour and it takes me 1/2 hour to drive to and from the faraway station. For simplicity, assume the travel cost to the local station is zero miles and damage/depreciation of my car is trivial on the trip to the faraway station. Should I buy my gas at the faraway station