Concerning speed of service in the logistical system, which of the following is(are) accurate?
a. The longer the delivery time, the more inventory customers must maintain to service their needs while the shipment is in transit.
b. The slower modes of transportation involve higher variable costs for product movement.
c. The faster modes of transportation result in the need for higher investments in inventory by customers.
d. all of the above
e. both (b) and (c)
Answer: A