2. (5 credits) How does the speed of a runner vary over the course of a marathon (a distance of 42.195 km)? Consider determining both the time to run the first 5 km and the time to run between the 35-km and 40-km points, and then subtracting the former time from the latter time. A positive value of this difference corresponds to a runner slowing down toward the end of the race. The accompanying histogram is based on times of runners who participated in several different Japanese marathons ("Factors Affecting Runners' Marathon Performance," Chance, Fall, 1993: 24-30). 200- Frequency 150- 100- 50 Time difference -100 0 100 200 300 400 500 600 700 800 a) What are some interesting features of this histogram? (3 credits) b) Roughly what proportion of the runners ran the late distance more quickly than the early distance? (2 credits)