Martin bikes at a constant speed to a finish line that is 15 mi away. After 20 mins, he is 10 mi from the finish line. After 30 mins, he is 7.5 mi from the finish line. If a graph shows his distance y from the finish line, in miles, after x minutes, what Is the slope of the graph, and What does it represent?
A 15; Martin's initial distance
from the finish line
B 15; Martin's final distance from the finish line
C -0.25; the rate at which
Martin's distance from the
finish line changes per minute
D 0.25; the rate at which Martin's distance from the start line changes per minute