A certain gas pollution in the Russia has been issued for many years with mean μ = 34 ppm and standard deviation σ = 8 ppm. A group of car companies discharge gas into the air is now claiming that they have lowered the average with new clean devices. A group of community will test to see whether it is true at the level of significance (0.04). The sample size is 50 of a mean of 32.5 ppm. Elaborate a hypothesis test at the level of significance and state your decision.