Task: Question Answering
Input (English): Problem: for any non - zero a and b that satisfy | ab | = ab and | a | = a | b - 4 | + | ab - b | = ? 
Options: a ) ab - 4 , b ) 2 b - ab - 4 , c ) ab + 4 , d ) ab - 2 b + 4 , e ) 4 - ab
Output (English): a