Task: Question Answering
Input (English): Problem: gold is 19 times as heavy as water and copper is 9 times as heavy as water . in what ratio should these be mixed to get an alloy 13 times as heavy as water ? 
Options: a ) 1 : 2 , b ) 2 : 3 , c ) 4 : 1 , d ) 5 : 2 , e ) 6 : 5
Output (English): b