NDA English Rearranging Sentences in a Paragraph

S1: At the roadside the driver will be asked to blow through a small glass tube into a plastic bag.
S6: The driver will be asked to go to the police station.
P : And if the colour change does not reach the line the driver cannot be punished under the new law.
Q : Inside the tube are chemically treated crystals which change colour if the driver has alcohol on his breath.
R : But if the colour change does reach the line then the test has proved positive.
S : If the colour change goes beyond a certain line marked on the tube this indicates that the driver is probably over the specified limit.
The proper sequence should be