D. what is the cost for the 3% highest domestic airfares? (rounded to nearest dollar)

Assuming a standard deviation of $110 and normal distribution for domestic airfare, and a mean cost of $385, P (Z > x) = 0.03 Value of z to the cumulative probability of 0.03 from normal table is 1.88 P (x-u / (s. d) > x - 385/110) = 0.03 That is, (x - 385/110) = 1.88 - - > x = 1.88 * 110+385 = 591.91