Band 6+: The graph below shows changes in average monthly cost (euros) of four kinds of mobile contracts in a particular country in 2012. Summarise the information by selecting and reporting the main features and make comparisons where relevant. Write at least 150 words.

The image shows a line graph of average monthly costs in euros for four mobile contracts from December to August: Demo, Alpha, Slim, ETX. Demo starts at 23 in December, maintains through January, increases to 26 in February, peaks at 27 in March, stabilizes around 28 in April and May, rises to 31 in June, peaks at 33 in July, and drops to 32 in August. Alpha begins at 27 in December, drops to 24 in January, peaks at 28 in March, declines to 26 in April, stabilizes around 25 from May to June, then consistently increases, reaching 29 in July and August. Slim starts at 21 in December, declines to 19 in February, peaks to 22 in March, increases to 25 in April, rises to 28 in May, stabilizes by June between 27 and 28, peaks at 30 in July, dropping to 29 in August. ETX begins at 13 in December, peaks at 14 in March, drops to 10 by April, maintains from May to July, and increases to 12 in August.