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: given f ( x ) = 3 x – 5 , for what value of x does 2 * [ f ( x ) ] – 10 = f ( x – 2 ) ? 
Options: a ) 1 , b ) 2 , c ) 3 , d ) 4 , e ) 5
Example Output: c

Example Input: Problem: what is the average of first 21 multiples of 5 ? 
Options: a ) a ) 70 , b ) b ) 77 , c ) c ) 55 , d ) d ) 81 , e ) e ) 82
Example Output: c

Example Input: Problem: at company x , senior sales representatives visit the home office once every 15 days , and junior sales representatives visit the home office once every 10 days . the number of visits that a junior sales representative makes in a 2 - year period is approximately what percent greater than the number of visits that a senior representative makes in the same period ? 
Options: a ) 10 % , b ) 25 % , c ) 33 % , d ) 50 % , e ) 67 %
Example Output:
d