Detailed Instructions: In this task, you need to answer the given multiple-choice question on the gain. Gain is the value by which to multiply the input. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
Q: Problem: at what rate percent per annum will a sum of money double in 16 years . 
Options: a ) 2.45 % , b ) 5.62 % , c ) 5.35 % , d ) 6.9 % , e ) 6.25 %
A:
e