Levi and Rachel performed an experiment in which they measured the heart rate of an average adult. On one day, Levi measured the resting heart rate of an adult. Then, the adult walked on a treadmill at a rate of four miles per hour. After thirty minutes, he measured the adult's heart rate again and recorded the data. Levi allowed the adult's heart rate to return to its original resting rate and then repeated his experiment two more times. Two days later, Rachel performed the same experiment with the same adult. She, too, measured the resting heart rate and the heart rate after exercising. Their data appears below.