Task: Question Answering
Input (English): Problem: the avg weight of a , b & c is 84 kg . if d joins the group , the avg weight of the group becomes 80 kg . if another man e who weights is 3 kg more than d replaces a , then the avgof b , c , d & e becomes 79 kg . what is the weight of a ? 
Options: a ) 45 , b ) 65 , c ) 75 , d ) 89 , e ) 90
Output (English): c