When Helen jogs, every 20 minutes she checks the total distance she traversed. One day, the first time she checked, Helen had jo
gged a distance of 2.5 miles, the second time she checked, she had jogged a total distance of 4.8 miles, and the third and final time that she checked, Helen found out that she jogged a total distance of 6.8 miles. What is the difference between her average speeds, in miles per hour, during the first 20 minutes of jogging and the last 20 minutes of jogging?
