The given line graph tracks in detail the fluctuations of the average monthly charges of four distinct mobile contract types in a specific country in 2012.
Looking from an overall perspective，two out of the four mobile service providers—namely Demo and Alpha both demonstrated a general upward trend in terms of their monthly cost while the remaining two — Silm and ETX experienced relatively stable pricing although minor fluctuations were observed throughout the year.
In detail，it is clear that Demo remained consistently the most expensive service provider throughout the year. From an initial 22 euros in December to a historic low of 20 euros in February，the monthly cost of Demo then experienced a continuous rising tendency and reached 32 euros in July before it dipped to 30 in August. Alpha，as the second most costly provider，experienced a similar downward trend as Demo at the beginning of the year，with its monthly service charges slipping back to 16 euros in January from the original 18 euros. After that，the monthly cost of it also exhibited a considerable rising inclination and arrived at a little more than 25 euros in August despite a minor fall between March and April.
At the meantime，customers of the other two brands — Silm and ETX experienced several changes regarding the service expenditures on a monthly basis. To be more specific，Silm charged its clients at about 16 euros per month in December and at a surprising low of 12 in June before the monthly cost of the company bounced back to the original 16 in December. Notably，the monthly charges of ETX was，at all times the lowest among the four companies throughout the year. Although the monthly expenses had a record high of 12 in June from the initial 9 euros a month，it continuously kept declining at arrived at an unprecedented low of only 8 in August.