Theresa ran on a treadmill for thirty minutes, and her time and speed are shown on the graph above. The x-axis represents time (in minutes), and the y-axis represents speed (in miles per hour).
Which of the following statements about Theresa's run is true?
Theresa's speed was increasing for a total of 15 minutes.
The rate of speed increase from 0 to 5 minutes was less than the rate of speed decrease from 25 to 30 minutes.
Theresa reached her maximum speed at 20 minutes.
Theresa's speed was constant for a longer period than it was increasing.
