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: a cyclist rides a bicycle 8 km at an average speed of 10 km / hr and again travels 10 km at an average speed of 8 km / hr . what is the average speed for the entire trip ? 
Options: a ) 9.28 , b ) 8.48 , c ) 8.78 , d ) 8.98 , e ) 9.18
Example Output: c

Example Input: Problem: ? x 24 = 173 x 240 
Options: a ) 545 , b ) 685 , c ) 865 , d ) 1730 , e ) 534
Example Output: d

Example Input: Problem: a telephone company needs to create a set of 3 - digit area codes . the company is entitled to use only digits 2 , 4 and 5 , which can be repeated . if the product of the digits in the area code must be even , how many different codes can be created ? 
Options: a ) 20 , b ) 22 , c ) 24 , d ) 26 , e ) 30
Example Output:
d