Task: Question Answering
Input (English): Problem: we have boxes colored either red or blue . in each blue box there is a fixed number of blueberries . in each red box there is a fixed number of strawberries . if we dispose of one blue box for one additional red box , the total number of berries would increase by 10 , and the difference between the total number of strawberries and the total number of blueberries would increase by 50 . each blue box contains how many blueberries ? 
Options: a ) 10 , b ) 15 , c ) 20 , d ) 25 , e ) 30
Output (English): c