Task: Question Answering
Input (English): Problem: a mixture contains milk and water in the ratio 5 : 2 . on adding 10 liters of water , the ratio of milk to water becomes 5 : 3 . the quantity of milk in the original mixture is ? 
Options: a ) 30 , b ) 40 , c ) 50 , d ) 60 , e ) 70
Output (English): c