Assume that the average annual salary for a worker in the US is 31,000 and that the annual salaries for Americans are normally distributed with a standard d equal to 7,000. Find the following: a) what % of Americans earn below 20,000 b) what % of Americans earn above 45,000 Solution a) P(x < 20000) = P( z < (20000-31000)/7000) = 0.058 = 5.8% b)P(x > 45000) = P( z > (45000-31000)/7000) = 0.0228 = 2.28%.