This question consists of six sentences of a passage. The first and sixth sentences are given as S1 and S6. The middle four sentences in each have been jumbled up and labelled as P, Q, R and S. You are required to find the proper sequence of the four sentences and mark your response accordingly.

S1: Southern Railway (SR) has prepared and submitted a detailed project report (DPR) to the Railway board to increase the speed in the Chennai-Bengaluru section to 160 kmph.
P: It also prepared DPR for Chennai-Gudur and Chennai-Renigunta sections for 160 kmph, and submitted to the Railway Board.
Q: The Railway Board had approved in principle the upgradation of speed to 160 kmph in eight routes of Indian Railways.
R: According to a press release, various zonal railways were nominated as nodal railways for the preparation of DPR.
S: The average speed in the two sections is around 130 kmph.
S6: In the Chennai-Renigunta section, works for speed enhancement from the existing 110 kmph to 130 kmph were completed.