Task: Question Answering
Input (English): Problem: in what ratio must tea at rs . 60 per kg be mixed with tea at rs . 70 per kg so that the mixture must be worth rs . 67.5 per kg ? 
Options: a ) 3 : 1 , b ) 3 : 2 , c ) 4 : 3 , d ) 1 : 3 , e ) none
Output (English): d