Q: 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'.
Problem: 1 = 5,2 = 4,3 = 253,4 = 2,6 = 15 , then 15 = ? 
Options: a ) 1 , b ) 255 , c ) 345 , d ) 445 , e ) 6
A:
e