A regional airline carrier determined that the number of kilo meters travelled per airplane per year is normally distributed with a mean of 700 thousand kilo meters and a standard deviation of a 100 thousand kilo meters.

a. What percentage of the planes is expected to travel between450 and 700 thousand kilo meters in a year?

b. What proportion of the planes is expected to travel between350 and 600 thousand kilo meters in a year?

c. Find the distance in kilo meters travelled by 70% of the planes.

d. Compare the answers of parts

(a) through

(c) if the standard deviation is 80 thousand kilo meters.