Understanding FCE Writing Part 1 tasks

It is important that the candidates understand the following points about Part 1:
it is compulsory
it consists of a transactional letter in response to a request for action, or to initiate action. It will lead to further action on the part of the recipient of the letter.
the letter may be formal or informal, the instructions will make it clear which style is more appropriate
the letter should include normal letter-writing conventions
the letter has to be based on input in the form of text, notes and possibly illustrations
all points in the input must be covered in the candidate's letter
the aim of the task is to achieve a positive effect on the target reader