Rachel hikes at a steady rate from a ranger station to a campground that is 20 mi away. After 2 h, she is 13 mi from the campground. After 4 h, she is 6 mi from the campground. A graph shows her distance from the campground y, in miles, after x hours. What is the slope of the graph, and what does it represent? A. 20; Rachel's initial distance from the campground
B. −3.5; the rate at which Rachel's distance from the campground changes per hour
C. 3.5; Rachel's initial distance from the campground
D. 20; Rachel's final distance from the campground