Task: Question Answering
Input (English): Problem: in a class of 60 students , 20 did not opt for math . 15 did not opt for science and 5 did not opt for either . how many students of the class opted for both math and science ? 
Options: a ) 23 , b ) 25 , c ) 27 , d ) 30 , e ) 48
Output (English): d