Use the following information to answer questions 46-49.

A balloonist collecting data on pollutants at various levels above the ground takes off at 8:00 A.M. When the balloon is in motion, it moves only straight up or straight down and at a constant speed within each hour-long interval. The balloon is at an altitude that is a multiple of 100 meters at the beginning of each hour. The balloon lands at 2:00 P.M. at the same spot from which it took off. The altitude of the balloon, in meters above the ground, is shown in the figure below.