The function y = 4x represents the distance in miles, y, a horse runs in x hours.
What does the average rate of change over the interval [5, 7] mean?
A. The average speed of the horse in hours per mile between hours 5 and 7.
B. The average speed of the horse in miles per hour between hours 5 and 7.
C. The total time the horse travels in hours between hours 5 and 7.
D. The total distance the horse travels in miles between hours 5 and 7.