The level of a pollutant in a river adjacent to a chemical plant is monitored periodically. Over a period of years, the normal level of the contaminant has been established by chemical analysis. The company has recently made several changes to the plant that appear to have increased the level of the contaminant. The Environmental Protection Agency (EPA) wants conclusive proof that the level of pollutants has not increased. State the null and alternative hypotheses relevant to this situation. Choose which sign applies? HO: current (