“四倍”的英语？

过去五年中，销售额已增长至以前的四倍。Sales have quadrupled in the last five years.过去几年中销售量较原来的增加了四倍。Sales have quintupled over the past few years.这座城市的空气污染程度曾高达可接受标准的四倍.Air pollution in the city had reached four times the acceptable level...