•Juanita Princepiohas recorded the costs of an automatic guided vehicle (AGV) that moves materials around an assembly hall.
•The longer the AGV works without maintenance, the higher are the expected failure costs (shown below).
•The maintenance also affects the resale value, giving a varying capital charge.
•Preventive maintenance can be done at a cost of £1000 and this brings the AGV back to new condition.
1.What is the best time between maintenance periods?