The ACME Stinker was an automobile that is no longer in production. When driven in city traffic, the nitrogen oxide levels it emitted adhered approximately to a normal distribution with mean 2.1 grams...

The ACME Stinker was an automobile that is no longer in production. When
driven in city traffic, the nitrogen oxide levels it emitted adhered approximately to
a normal distribution with mean 2.1 grams per mile and standard deviation 0.3
grams per mile.
a. By EPA mandate, nitrogen oxide levels were not to exceed 2.7 grams per
mile. About what proportion of Stinkers were in violation?
b. At most 25% of Stinkers exceeded what nitrogen oxide level?
c. ACME was forced to reduce the nitrogen oxide emissions level so that no
more than 1% of Stinkers exceeded 2.7 grams per mile. If the standard
deviation remained at 0.3 grams per mile, to what value did the mean
emissions level have to be reduced?