The graph below shows the number of enquiries received by the Tourist Information Office in one city over a six month period in 2011 Summarize the information by selecting and reporting the main features and make comparisons where relevant

The line graph illustrates how many enquiries the Tourist Information Office of a city received from January to June in the year 2011.
Overall, there was an increase in the number of enquiries sent by telephone and in person. In contrast, fewer people used letter or email to contact to the Tourist Information Office during the given period.
At the beginning of the year, over 400 enquiries received by the office, while the figures for contacts through letter/ email and telephone were significant higher than that, at about 800 and 900 respectively. In the next two months, there was a double rise in the number of in person enquiries received, which further went up continuously to reach the highest peak at over 1800 in June.
The number of enquiries sent by telephone also increased double, from over 800 in Jan to 1600 in Jun although being experienced a slight decrease in February. However, the quantity of letter/email enquiries reduced gradually from Jan to March, before hitting a free fall down to nearly 400 at May.