Average speed is found by dividing the distance traveled by the time taken. Suppose a runner checks her smartwatch during a run and finds she has traveled 1.53 miles after 12.3 minutes. She checks again after finishing and she traveled a total of 3.24 miles in 27.2 minutes. Find the runner's average speed (in mi/min) for (a) the first part of the run (b) the second part of the run (c) the entire run.