Task: Question Answering
Input (English): Problem: a tradesman sold an article at a loss of 20 % . if the selling price had been increased by $ 100 , there would have been a gain of 5 % . what was the cost price of the article ? 
Options: a ) $ 100 , b ) $ 200 , c ) $ 300 , d ) $ 400 , e ) $ 500
Output (English): d