The following six sentences come from a paragraph. The first and the last sentences are given. Choose the order in which the four sentences (PQRS) should appear to complete the paragraph.
S1: Convention has a necessary part to play in the life of everyone.
S6: Their purpose, however, is always the same.
P: It is necessary and useful for this reason.
Q: Of course, there is nothing absolute about conventions.
R: They vary from country to country, from age to age.
S: In all social affairs it prescribes more or less generally accepted rules of behaviour.
The proper sequence should be: