Task: Question Answering
Input (English): Problem: a watch was sold at a loss of 10 % . if it was sold for rs . 500 more , there would have been a gain of 10 % . what is the cost price ? 
Options: a ) 1000 , b ) 2998 , c ) 2500 , d ) 2788 , e ) 2991
Output (English): c