Task: Question Answering
Input (English): Problem: in what ratio water be mixed with milk costing rs . 12 per liter to obtain a mixture worth of rs . 8 per litre ? 
Options: a ) 2 : 7 , b ) 1 : 2 , c ) 2 : 9 , d ) 2 : 2 , e ) 2 : 6
Output (English): b