In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: what is the next number 12 13 15 17 111 113 117 119 123 129 ? 
Options: a ) 154 , b ) 220 , c ) 129 , d ) 131 , e ) 224
Example Output: d

Example Input: Problem: total 85 matches are conducted in knockout match type . how many players will be participated in that tournament ? 
Options: a ) 85 , b ) 81 , c ) 53 , d ) 82 , e ) 84
Example Output: e

Example Input: Problem: a customer bought a product at the shop . however , the shopkeeper increased the price of the product by 10 % 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 ) 12 % , c ) 14 % , d ) 16 % , e ) 18 %
Example Output:
b