Task: Question Answering
Input (English): Problem: the average of 9 observations was 6 , that of the 1 st of 5 being 10 and that of the last 5 being 8 . what was the 5 th observation ? 
Options: a ) 36 , b ) 12 , c ) 15 , d ) 17 , e ) 18
Output (English): a