The language of graphs

The graph depicted the average daily us of D.C. Metro. The number of commuters increased to 200 at 7:00, then reached a peak at 8:00, whcih indicating the rush hour for people go to work or school. From 8:00 to 10:00, the number decreased to 200 and then slightly went up to 300 at 12:00. The number then remained a plateau to 14:00 and further plunged sharply to 100 at 16:00. After that, the number suddently surged to a peak to 400 commuters per hour at 18:00, which consisting with the time that people get off their work and come back to their home. Afterward, the number of commuters dramatically declined to 100 and then remained steady until the end of metro service at 22:00. In conclusion, we can tell that there are two peaks in the graph. One is at 8:00; the other is at 18:00. After the first peak, the number stabilized and remained constant from 12:00 to 14:00. After the second peak, the number of commuters stabilized again and was eventually unchanged.