Task: Question Answering
Input (English): Problem: 3 maths classes : a , b and c take an algebra test . the average score of class a is 83 . the average score of class b is 76 . the average score of class c is 85 . the average score of class a and b is 79 and average score of class b and c is 81 . what is the average score of classes a , b , c ? 
Options: a ) 81.8 , b ) 81.1 , c ) 81.2 , d ) 81.5 , e ) 81.9
Output (English): d