The graph shows the relationship between the number of minutes Maria spent jogging on a treadmill and the distance she jogged.

A graph titled Miles on the Treadmill. The x-axis shows number of minutes, numbered 5 to 45, and the y-axis shows distance in miles, numbered 1 to 9. A straight line with a positive slope begins at point (0, 0) and ends at point (45, 4.5).
What was her speed?