石油化工产品现在已占所有化学制品的四分之一，十年后预计这个数目还要加倍。 Petrochemicals today account for one fourth of all the chemicals made, in ten years this amount is expected to double.
计算机在检查了16000种可能的设计方案之后，选出了以最低的成本生产最多化工产品的工厂的设计方案。 After running through16,000 possible designs, the computer picked out the plan for the plant that would produce the most chemicals at the lowest cost.
