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'.

[EX Q]: Problem: a = 4 ^ 15 - 625 ^ 3 and a / x is an integer , where x is a positive integer greater than 1 , such that it does not have a factor p such that 1 < p < x , then how many different values for x are possible ? 
Options: a ) none , b ) one , c ) two , d ) three , e ) four
[EX A]: c

[EX Q]: Problem: if 5400 mn = k ^ 4 , where m , n , and k are positive integers , what is the least possible value of m + 2 n ? 
Options: a ) 11 , b ) 18 , c ) 20 , d ) 25 , e ) 40
[EX A]: e

[EX Q]: Problem: half a number plus 5 is 13 . what is the number ? 
Options: a ) 8 , b ) 16 , c ) 10 , d ) 11 , e ) 12
[EX A]:
b