Find the Average Rate of Change Illustrated in the Graph

Multiple Choice

Find the average rate of change illustrated in the graph.
-A deep sea diving bell is being lowered at a constant rate. After 8 minutes, the bell is at a depth of 400 ft. After 45 minutes the bell is at a depth of 1800 ft. What is the average rate of change of depth?
Round to one decimal place.

A) 40.0 ft per minute
B) 31.1 ft per minute
C) 37.8 ft per minute
D) 0.03 ft per minute