In the following items, each passage consists of six sentences. The first sentence (S1) and the final sentence (S6) are given. The middle four sentences in each have been removed and jumbled up. These are labelled P, Q, R and S. You are required to find out the proper sequence of the four sentences and mark accordingly on the Answer Sheet. 

S1: The oil found in natural state is called crude oil. 
P: It is used as a fuel in heaters and lamps.
Q: It is treated in refineries, the most common form of treatment is heating. 
​R: Gas that comes off the oil later is condensed into paraffin. 
S: When crude oil is heated, the first vapours to rise are cooled and become the finest petrol. 
S6:  Last of all, the lubricating oils of various grades are produced.