Task: Question Answering
Input (English): Problem: the ratio of red balls to blue balls is 3 : 7 . 70 % of the red balls and 30 % of the blue balls are tennis balls . how many of the balls are tennis balls ? 
Options: a ) 44 % , b ) 40 % , c ) 45 % , d ) 42 % , e ) 48 %
Output (English): d