Task: Question Answering
Input (English): Problem: a tradesman sold an article at a loss of 10 % . if the selling price had been increased by $ 50 , there would have been a gain of 10 % . what was the cost price of the article ? 
Options: a ) $ 150 , b ) $ 200 , c ) $ 250 , d ) $ 120 , e ) $ 100
Output (English): c