A manufacturer of goods uses two factors to decide whether to use truck or rail for movement of its products to market: cost and total travel time. The manufacturer uses a utility formula that rates each mode. The utility formula is U = 5C +10T, where C is cost ($/ton) and T is time (hours). For a given shipment of goods, a trucking firm can deliver in 16 hours and charges $25/ton, whereas a railroad charges $17/ton and can deliver in 25 hours.

Required:
a. What other factors should the shipper take into account in making this decision?
b. Which mode should the shipper select?