Subject: mathqa
Question: 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 ?
Option: 
A: 6 %
B: 8 %
C: 2 %
D: 4 %
Answer: D