Task: Question Answering
Input (English): Problem: if the sides of a cube are in the ratio 5 : 4 . what is the ratio of their diagonals ? 
Options: a ) 4 : 3 , b ) 5 : 4 , c ) 4 : 7 , d ) 3 : 4 , e ) 4 : 5
Output (English): b