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: if a ' s salary is 20 % less than b ' s salary , by how much percent is b ' s salary more than a ' s ? 
Options: a ) 5 % , b ) 10 % , c ) 15 % , d ) 25 % , e ) none
Example Output: d

Example Input: Problem: for any integer k greater than 1 , the symbol k * denotes the product of all integers between 1 and k , inclusive . if k * is a multiple of 315 what is the least possible value of k ? 
Options: a ) 5 , b ) 7 , c ) 9 , d ) 11 , e ) 13
Example Output: b

Example Input: Problem: john want to buy a $ 100 trouser at the store , but he think it ’ s too expensive . finally , it goes on sale for $ 50 . what is the percent decrease ? 
Options: a ) 20 % , b ) 30 % , c ) 50 % , d ) 70 % , e ) 80 %
Example Output:
c