Task: Question Answering
Input (English): Problem: of 300 surveyed students , 20 % of those who read book a also read book b and 50 % of those who read book b also read book a . if each student read at least one of the books , what is the difference between the number of students who read only book a and the number of students who read only book b ? 
Options: a ) 120 , b ) 125 , c ) 130 , d ) 135 , e ) 150
Output (English): e