Task: Question Answering
Input (English): Problem: a customer bought a product at the shop . however , the shopkeeper increased the price of the product by 20 % so that the customer could not buy the required amount of the product . the customer managed to buy only 80 % of the required amount . what is the difference in the amount of money that the customer paid for the second purchase compared to the first purchase ? 
Options: a ) 10 % , b ) 8 % , c ) 6 % , d ) 4 % , e ) 2 %
Output (English): d