The function shown below was created to track the different intervals of speed that an automobile travels over a period of 28 seconds. Use the graph of the function to complete Parts 1-3.

After traveling for 16 seconds, the automobile begins to slow its speed at a steady rate. Use the coordinates on the graph to determine the rate at which the car is slowing down, in miles per hour per second.
During which interval of time does the automobile experience the greatest change in its speed? What is the change in the automobile's speed during this interval?
For a time period of approximately 10 seconds, the automobile experiences no change in its speed. During which interval of time does the automobile's speed remain constant? At what speed is the automobile traveling during this interval?