31) Why is it that many cases of infant mortality of products are not due to product failure? 32) What is breakdown maintenance? 33) Explain why a small standard deviation of the MTBF distribution makes a product, machine, or process a good candidate for preventive maintenance while a large standard deviation does not. 34) Why is it that many cost curves associated with maintenance rarely consider the full cost of a breakdown? 35) Is there an optimal amount of preventive maintenance? What caution should be exercised before calculating this optimal amount?