Task: Question Answering
Input (English): Problem: a mixture contains alcohol and water in the ratio 4 : 3 . if 10 litres of water is added to the mixture , the ratio becomes 4 : 5 . find the quantity of alcohol in the given mixture 
Options: a ) 15 litres , b ) 10 litres , c ) 30 litres , d ) 20 litres , e ) 8 litres
Output (English): d