An aircraft engine manufacturer has developed a new engine with better safety performance than the old engine. In the first year when both new and old models of the engine were sold at the same time, the sales of the old engine exceeded that of the new engine, and the manufacturer concluded that It is concluded that security is not a top priority for customers. Which of the following, if true, would most seriously undermine the manufacturer's conclusions? ? ['There is no particularly large price difference between new and old engines.', 'New engines can be used by all aircraft using older engines.', 'Both private jet owners and airlines buy engines from this aircraft engine maker.', 'Customers believe that older engines are better than newer models in terms of safety because they know more about the safety of older engines.']