It s true sand dunes in Colorado rival sand dunes of the Great Sahara Desert The highest dunes at Great Sand Dunes National Monument can exceed the highest dunes in the Great Sahara extending over 700 feet in height However like all sand dunes they tend to move around in the wind This can cause a bit of trouble for temporary structures located near the escaping dunes Roads parking lots campgrounds small buildings trees and other vegetation are destroyed when a sand dune moves in and takes over Such dunes are called escape dunes in the sense that they move out of the main body of sand dunes and by the force of nature prevailing winds take over whatever space they choose to occupy In most cases dune movement does not occur quickly An escape dune can take years to relocate itself Just how fast does an escape dune move Let x be a random variable representing movement in feet per year of such sand dunes measured from the crest of the dune Let us assume that x has a normal distribution with 18 feet per year and a 3 2 feet per year USE SALT Under the influence of prevailing wind patterns what is the probability of each of the following Round your answers to four decimal places a an escape dune will move a total distance of more than 90 feet in 4 years X b an escape dune will move a total distance of less than 80 feet in 4 years c an escape dune will move a total distance of between 80 and 90 feet in 4 years