7. A warehouse of spare parts for old British sports cars like Morgan, MG, Jaguar, Triumph, Auston Healey, and so forth is located in Canada. It supplies car clubs, repair shops, and individuals throughout North America and, occasionally, other parts of the world. Replacement inventory is primarily ordered from Britain, but sometimes from dealers in other parts of the Commonwealth (e.g., Australia, New Zealand, etc.). In determining demand during lead time, what could cause uncertainty in demand and what could cause it in lead time?