` S_(1)` : When the Romans in vaded Britain about, 2,000 yars ago, their calender was caculated on the phases of the moon.
`S_(6)` : The astronomer's name was Sosigenes and his caendar had a year of 365 days.
P : This calender had gradually becomes so out of line wiht the seasons that it was to or three monts behind.
Q : The Emperor Julies Caser was determined to correct it.
R : Caser had been to Egypt and seen the davantages of a calender which used only the sun.
S : So he sought help form a Greek astronomer who lived in the Egyptian city of Alexandria.
Which one of the following is the correct sequence?