Answer:
The correct answer is 30
Step-by-step explanation:
Given: The x-axis represents the time in hours and the y-axis represents the distance in miles.
The line passes through the points
and 
To find: The rise-over-run value for the relationship in the graph.

Thus, the rise-over-run value for the relationship represented in the graph is 30.
Answer = The string would be 4pi feet longer than the Earth's circumference at the surface at about 12.5 feet.
(hope this helps)