The level of nitrogen oxides in the exhaust of cars of a particular model varies normally with a mean of 0.2 grams per mile (g/mi) and a standard deviation of 0.05 g/mi. Government regulations call for nitrogen oxide emissions no higher than 0.4g/mi.
a)What is the probability that a single car of this model fails to meet the nitrogen emissions regulations
b) a company has 25 cars of this model. What is the probability that the mean nitrogen oxide emissions of these cars is above the 0.3g/mi limit?