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: Newton was perhaps the greatest scientist that ever lived. 
P: But when he was only 22, a terrible plague epidemic swept · over England. 
Q: He was the son of a Lincolnshire farmer, and born in 1642. 
R: Therefore the universities were closed.
S: He went to Cambridge to study mathematics when he was 19. 
S6: Newton went home and worked . quietly by himself for about 18 months.