The line graph depicts the changes in the average charge in each month contacting across specific four cell phones in a European country during nine months starting with January 2002.
Overall, it is apparent that the Alpha, Lex and Domo mobiles exhibited an upward trend in its connecting rate throughout the months. In contrast, the rest of Sim TX type experienced fluctuations. The rest of Domo cell phone maintained a dominant position for most of the month.
In January, the Domo mobile had the highest proportion contacting, with 15 euro of its phone being consumed. It underwent a slight fluctuate plunging to around 20 euro from may and Jun, and remained stable at this level. Before decreasing to just more than 23 euro at the end of the period, its revenue reaching a peak of 25 euro. Interestingly, botj the rest of Alpha and Lex cell phones started with 5 and more than 7 euro in the first month (January), after oscillating during 5 months later, which got around below 10 euro and 15 euro, respectively. Even though having slightly increased around 10 euro, Alpha over taking 3 others type of mobile to reach a highest revenue (25 euro) in September.
Concerning with Sim TX mobile, which was stayed at 9 euro in January and maintained around 14 euro in 5 months from the former time. However, the proportion of contracting of this kind cell phone gradually increased. This upward trend continued, peaking of 14 euro in Jun, before climbing to 8 euro in last month.