Data regarding fuel efficiency of an airliner were collected. The graph shows the correlation between the distance traveled (in thousands of miles) and the altitude (in thousands of feet):

image of a scatter plot with Distance Traveled on the x axis and Altitude on the y axis with 2 comma 2, 3 comma 10, 5 comma 15, 10 comma 20, 15 comma 15, 18 comma 10, and 19 comma 2

Estimate the average rate of change from x = 15 to x = 19.