Refer to Exercise 33. A random sample of 2 years is selected. Find the probability that the mean amount of black carbon emissions for the sample is 

(a) Less than 12.3 gigagrams per year, 

(b) Between 15.4 and 19.6 gigagrams per year, and 

(c) Greater than 17.7 gigagrams per year. Compare your answers with those in Exercise 33.

Find the indicated probabilities and interpret the results.

Data from exercise 33:

Yearly amounts of black carbon emissions from cars in India are normally distributed, with a mean of 14.7 gigagrams per year and a standard deviation of 11.5 gigagrams per year. Find the probability that the amount of black carbon emissions from cars in India for a randomly selected year are

(a) Less than 12.3 gigagrams per year.

(b) Between 15.4 and 19.6 gigagrams per year.

(c) Greater than 17.7 gigagrams per year.