In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

[EX Q]: Problem: for each 6 - month period during a light bulb ' s life span , the odds of it not burning out from over - use are half what they were in the previous 6 - month period . if the odds of a light bulb burning out during the first 6 - month period following its purchase are 1 / 5 , what are the odds of it burning out during the period from 6 months to 1 year following its purchase ? 
Options: a ) 5 / 27 , b ) 2 / 9 , c ) 1 / 2 , d ) 4 / 9 , e ) 2 / 3
[EX A]: c

[EX Q]: Problem: the mean of 50 observations was 36 . it was found later that an observation 48 was wrongly taken as 23 . the corrected new mean is : 
Options: a ) 36.5 , b ) 35 , c ) 34 , d ) 33 , e ) 32.5
[EX A]: a

[EX Q]: Problem: sophia finished 2323 of a book . she calculated that she finished 90 more pages than she has yet to read . how long is her book ? 
Options: a ) 140 , b ) 320 , c ) 745 , d ) 270 , e ) 350
[EX A]:
d